Q1. What is a luminous object?
a) An object that reflects light
b) An object that absorbs light
c) An object that emits light
d) An object that changes light into another form of energy
Answer: c) An object that emits light
Explanation: Luminous objects are those that emit light of their own. Examples include the Sun and a torch bulb. They are the sources of light that enable us to see other objects.
Q2. Which of the following materials is typically transparent?
a) A wooden board
b) A piece of rock
c) A sheet of plane glass
d) A sheet of cardboard
Answer: c) A sheet of plane glass
Explanation: Transparent materials allow light to pass through them without significant scattering, enabling us to see clearly through them. A sheet of plane glass is a common example of a transparent material.
Q3. The formation of shadows requires which of the following conditions?
a) A luminous object and a screen
b) An opaque object and a source of light
c) A transparent object and a screen
d) A translucent object and a source of light
Answer: b) An opaque object and a source of light
Explanation: Shadows are formed when an opaque object obstructs the path of light from a source, such as the Sun or a torch. The shadow is the area where light is blocked by the object.
Q4. What is a pinhole camera?
a) A camera with a large lens
b) A camera that uses a pinhole to form an image
c) A camera that captures moving images
d) A camera with multiple lenses
Answer: b) A camera that uses a pinhole to form an image
Explanation: A pinhole camera is a simple camera without a lens but with a tiny aperture (a pinhole). It projects an inverted image on the opposite side of the box, demonstrating basic principles of optics.
Q5. Which of the following objects would likely be translucent?
a) A mirror
b) Tracing paper
c) A piece of aluminium
d) Water
Answer: b) Tracing paper
Explanation: Translucent materials allow light to pass through them but scatter it in the process, making objects on the other side not clearly visible. Tracing paper is an example of a translucent material.
Q6. During an eclipse, how can one safely view it using a pinhole camera?
a) By looking directly at the sun through the pinhole
b) By projecting the image of the sun onto a screen
c) By capturing the image on photographic film
d) By using a special lens in the pinhole
Answer: b) By projecting the image of the sun onto a screen
Explanation: A pinhole camera can be used to project an image of the sun onto a screen, allowing safe observation of an eclipse. It’s important never to look directly at the sun, even through a pinhole.
Q7. What happens to light when it strikes a mirror?
a) It is absorbed
b) It passes through
c) It is refracted
d) It is reflected
Answer: d) It is reflected
Explanation: When light strikes a mirror, it is reflected. Mirrors have smooth surfaces that reflect light in a consistent and predictable manner, allowing us to see our reflection.
Q8. What does the shadow of an object tell us?
a) The color of the object
b) The texture of the object
c) The shape of the object
d) The weight of the object
Answer: c) The shape of the object
Explanation: Shadows can provide information about the shape of an object. The shadow is a silhouette of the object and can sometimes be used to identify the object based on its outline.
Q9. What is the main reason we are not able to see objects in a completely dark room?
a) The objects do not emit light
b) The room absorbs all light
c) There is no source of light
d) The objects are transparent
Answer: c) There is no source of light
Explanation: Visibility of objects requires a source of light. In a completely dark room, the absence of a light source means that light rays are not available to reflect off objects and into our eyes, rendering them invisible.
Q10. How does the shadow of an object change with the position of the light source?
a) The shadow becomes transparent
b) The shadow’s color changes
c) The size and position of the shadow change
d) The shadow remains constant
Answer: c) The size and position of the shadow change
Explanation: The size and position of a shadow are dependent on the light source’s position relative to the object. As the angle and distance of the light source change, so do the length and orientation of the shadow.
Q11. What type of image is formed by a pinhole camera?
a) Inverted and real
b) Erect and real
c) Inverted and virtual
d) Erect and virtual
Answer: a) Inverted and real
Explanation: A pinhole camera forms an inverted and real image. The light rays pass through the small pinhole and project an image on the opposite side, which is upside down compared to the object.
Q12. When a beam of light falls on a mirror at an angle, what happens to the angle of reflection?
a) It is less than the angle of incidence
b) It is greater than the angle of incidence
c) It is equal to the angle of incidence
d) It is unpredictable
Answer: c) It is equal to the angle of incidence
Explanation: According to the law of reflection, the angle of reflection (the angle at which light bounces off the mirror) is equal to the angle of incidence (the angle at which light strikes the mirror).
Q13. What do you need to observe a shadow?
a) A source of light, an opaque object, and a screen
b) Only a source of light and a screen
c) Only an opaque object and a screen
d) Only a source of light and an opaque object
Answer: a) A source of light, an opaque object, and a screen
Explanation: To observe a shadow, three things are necessary: a source of light (to cast the shadow), an opaque object (to block the light), and a screen (like the ground, a wall, or any surface where the shadow is visible).
Q14. Which of the following is a characteristic of a translucent object?
a) It allows all light to pass through it
b) It does not allow any light to pass through it
c) It allows light to pass through it but not clearly
d) It reflects all light
Answer: c) It allows light to pass through it but not clearly
Explanation: Translucent materials allow some light to pass through them, but the light is scattered, making it impossible to see clearly through them.
Q15. In the context of the chapter, which of the following best defines reflection?
a) Absorption of light by an object
b) Bending of light as it passes from one medium to another
c) The bouncing back of light from a surface
d) The passing of light through an object
Answer: c) The bouncing back of light from a surface
Explanation: Reflection is the phenomenon where light bounces back when it hits a reflective surface, like a mirror. This is different from absorption or transmission of light.
Q16. Why can we see circular images of the Sun under a tree covered with leaves?
a) Due to the bending of light through leaves
b) Because leaves act as multiple pinholes
c) Due to reflection from the leaves
d) Because leaves absorb light
Answer: b) Because leaves act as multiple pinholes
Explanation: The gaps between the leaves of a tree act as multiple pinholes. Each pinhole projects a circular image of the Sun on the ground, similar to the way a pinhole camera works.
Q17. What happens to the length of a shadow when the light source is moved closer to the object?
a) The shadow becomes longer
b) The shadow becomes shorter
c) The shadow’s color changes
d) The shadow remains the same length
Answer: b) The shadow becomes shorter
Explanation: As the light source moves closer to an object, the shadow becomes shorter. This is because the angle of the light narrows, reducing the area of obstruction caused by the object.
Q18. When looking at a candle through a pipe, why can’t you see the candle after bending the pipe?
a) The candle goes out
b) Light travels in a straight line
c) The candlelight is too weak
d) The pipe absorbs the light
Answer: b) Light travels in a straight line
Explanation: The inability to see the candle after bending the pipe demonstrates that light travels in a straight line. Once the pipe is bent, the straight path of light from the candle to your eye is interrupted.
Q19. Which of the following best describes a mirror?
a) An object that emits light
b) An object that scatters light
c) An object that reflects light
d) An object that absorbs light
Answer: c) An object that reflects light
Explanation: A mirror is an object that reflects light. Mirrors have smooth surfaces that reflect light rays, allowing us to see our reflection or the reflection of other objects.
Q20. What can you infer about an object if its shadow is very sharp and clear?
a) The object is very close to the light source
b) The light source is very far from the object
c) The object is transparent
d) The light source is of low intensity
Answer: b) The light source is very far from the object
Explanation: A sharp and clear shadow indicates that the light source is relatively far from the object. This distance allows for a well-defined and sharp shadow as the light rays are more parallel.
Q21. What type of mirror is typically used in bathrooms and dressing rooms?
a) Concave mirror
b) Convex mirror
c) Plane mirror
d) Spherical mirror
Answer: c) Plane mirror
Explanation: Plane mirrors are typically used in bathrooms and dressing rooms as they provide a reflection that is the same size as the object and is not distorted.
Q22. How does a periscope work?
a) By refracting light through a lens
b) By reflecting light using mirrors
c) By emitting light
d) By transmitting light through fibers
Answer: b) By reflecting light using mirrors
Explanation: A periscope works by reflecting light using mirrors. It typically has two mirrors placed at 45-degree angles, which allow light to be redirected from one end of the periscope to the other, enabling the user to see over or around obstacles.
Q23. Why are pinhole images of the Sun circular, regardless of the shape of the pinhole?
a) Because the Sun is circular
b) Because all images are inherently circular
c) Because of the diffraction of light
d) Because of the reflection of light
Answer: a) Because the Sun is circular
Explanation: Pinhole images of the Sun are circular because the Sun itself is circular. The shape of the pinhole does not affect the shape of the image in this case, as the light source (the Sun) is much larger than the pinhole.
Q24. What phenomenon is demonstrated by seeing the image of a tree reflected in a pond?
a) Refraction of light
b) Absorption of light
c) Transmission of light
d) Reflection of light
Answer: d) Reflection of light
Explanation: Seeing the image of a tree reflected in a pond is an example of the reflection of light. The smooth surface of the water acts like a mirror, reflecting the image of the tree.
Q25. What is the role of tracing paper in a pinhole camera?
a) It acts as a lens to focus light
b) It captures the permanent image
c) It serves as a translucent screen to view the image
d) It filters the light passing through the pinhole
Answer: c) It serves as a translucent screen to view the image
Explanation: In a pinhole camera, tracing paper acts as a translucent screen. It allows light to pass through and displays the image formed by the pinhole, but it’s not transparent enough to see through clearly like a lens.
Q26. Why do we not observe a shadow in a completely dark room?
a) Because there is no light source to cast a shadow
b) Because all objects in the room are transparent
c) Because shadows can only form in the presence of white light
d) Because the walls of the room absorb all shadows
Answer: a) Because there is no light source to cast a shadow
Explanation: Shadows form when an object blocks light from a source. In a completely dark room, there is no light source to create a shadow.
Q27. Which of these objects is most likely to cast a clearly defined shadow?
a) A foggy glass pane
b) A thin curtain
c) A solid wooden door
d) A clear glass window
Answer: c) A solid wooden door
Explanation: A clearly defined shadow requires an opaque object, like a solid wooden door. Opaque objects do not allow light to pass through, thus casting a distinct shadow.
Q28. What does an upside-down image in a pinhole camera illustrate about light?
a) Light is absorbed by the pinhole
b) Light rays bend when passing through a pinhole
c) Light travels in straight lines and inverts the image
d) Light disperses when passing through a pinhole
Answer: c) Light travels in straight lines and inverts the image
Explanation: The upside-down image in a pinhole camera demonstrates that light travels in straight lines. As light travels through the small pinhole, it does not scatter but crosses paths, inverting the image on the opposite side.
Q29. What is the significance of the experiment involving a mirror and a torch in a dark room?
a) It shows how light can be absorbed by a mirror
b) It demonstrates that light can pass through a mirror
c) It illustrates the reflection of light from a mirror
d) It proves that mirrors can magnify light
Answer: c) It illustrates the reflection of light from a mirror
Explanation: The experiment with a mirror and a torch in a dark room illustrates the reflection of light. When light from the torch hits the mirror, it is reflected, redirecting the beam of light to another point in the room.
Q30. In what way do shadows formed by opaque objects differ from images formed by mirrors?
a) Shadows show the exact color of the object, whereas mirror images do not
b) Shadows are always black, while mirror images retain the object’s colors
c) Shadows form on a screen, while mirror images form in space
d) Shadows are always larger than the object, but mirror images are the same size
Answer: b) Shadows are always black, while mirror images retain the object’s colors
Explanation: Shadows formed by opaque objects are devoid of color and appear black or grey, depending on the intensity of the light source. In contrast, mirror images reflect the actual colors of the object.
Q31. What happens to the shadow of an object when the light source is moved further away?
a) The shadow becomes sharper
b) The shadow becomes blurrier
c) The shadow becomes larger
d) The shadow becomes smaller
Answer: c) The shadow becomes larger
Explanation: As the light source moves further away from the object, the shadow cast by the object becomes larger. This is due to the increasing angle at which the light hits the object, enlarging the shadow’s outline.
Q32. Which of the following scenarios best demonstrates the concept of a pinhole camera in nature?
a) The image of the moon on a lake at night
b) Circular images of the Sun under a tree with dense leaves
c) Reflection of mountains in a clear, still lake
d) The formation of a rainbow after rain
Answer: b) Circular images of the Sun under a tree with dense leaves
Explanation: The circular images of the Sun under a tree with dense leaves act like multiple pinhole cameras. The gaps between leaves allow light through small openings, creating pinhole images of the Sun on the ground.
Q33. What type of image does a plane mirror produce?
a) Inverted and real
b) Inverted and virtual
c) Erect and real
d) Erect and virtual
Answer: d) Erect and virtual
Explanation: A plane mirror produces an erect (upright) and virtual image. The image appears to be behind the mirror and is the same size as the object, but it cannot be projected onto a screen.
Q34. How does the color of an opaque object affect the color of the shadow it casts?
a) The shadow is the same color as the object
b) The shadow’s color varies depending on the object’s color
c) The shadow is always black or grey, regardless of the object’s color
d) The shadow is a lighter version of the object’s color
Answer: c) The shadow is always black or grey, regardless of the object’s color
Explanation: The color of an opaque object does not affect the color of the shadow it casts. Shadows are typically black or grey, as they are formed due to the absence of light, not the object’s color.
Q35. What causes the formation of shadows under a tree with leaves?
a) The reflection of light off the leaves
b) The absorption of light by the leaves
c) The scattering of light by the leaves
d) The blocking of light by the leaves
Answer: d) The blocking of light by the leaves
Explanation: Shadows under a tree with leaves are formed because the leaves block light from the Sun. The spaces between the leaves allow some light to pass through, creating patches of shadow and light.
Q36. What phenomenon is observed when the long side of a box is pointed towards the Sun, resulting in the shortest shadow?
a) Reflection
b) Refraction
c) Diffraction
d) Orientation effect on shadow length
Answer: d) Orientation effect on shadow length
Explanation: The orientation effect on shadow length is observed when the long side of a box is pointed towards the Sun. This orientation minimizes the angle at which sunlight strikes the box, resulting in the shortest shadow.
Q37. In a pinhole camera, why are images seen upside down?
a) Due to the reflection of light inside the camera
b) Because the pinhole inverts the light rays
c) Due to the refraction of light through the pinhole
d) Because light travels in straight lines and crosses over at the pinhole
Answer: d) Because light travels in straight lines and crosses over at the pinhole
Explanation: In a pinhole camera, images are seen upside down because light travels in straight lines. When light rays pass through the small pinhole, they cross over, causing the top of the object to be projected at the bottom and vice versa.
Q38. What is the primary use of a periscope?
a) To magnify distant objects
b) To view objects around corners or over obstacles
c) To project images onto a screen
d) To capture and save images
Answer: b) To view objects around corners or over obstacles
Explanation: The primary use of a periscope is to view objects around corners or over obstacles. It uses a set of mirrors or prisms to reflect light from one end to the other, allowing the user to see over or around obstructions.
Q39. What causes pinhole images of the Sun to appear during an eclipse?
a) The bending of light around the moon
b) The projection of the Sun’s image through natural pinholes
c) The reflection of the Sun’s image from the moon
d) The scattering of sunlight through atmospheric particles
Answer: b) The projection of the Sun’s image through natural pinholes
Explanation: During an eclipse, pinhole images of the Sun appear due to the projection of the Sun’s image through natural pinholes, like gaps between leaves. These pinholes act like tiny cameras, projecting the image of the Sun, which shows the eclipse progress.
Q40. What can you infer about the path of light based on the experiment of looking at a candle through a bent pipe?
a) Light can easily bend around corners
b) Light travels in a straight line
c) Light splits into colors when obstructed
d) Light gets absorbed by opaque materials
Answer: b) Light travels in a straight line
Explanation: The experiment of looking at a candle through a bent pipe demonstrates that light travels in a straight line. When the pipe is straight, you can see the candle because the light travels directly through the pipe. Once the pipe is bent, the light path is obstructed, and the candle is no longer visible.