Light is a form of energy. It passes through transparent material but not through opaque materials.A shadow is formed when light hits an opaque surface.Refelction occurs when the light comes in contac with a shuny surface.Let us understand this lesson with the help of important question answers on lighg, shadow and reflection.
Important question answers :
1. Classify the objects given below as opaque, transparent or translucent and luminous or non-luminous (Air, water, a piece of rock, a sheet of aluminum, a mirror, a wooden board, a sheet of polythene, a CD, smoke, a sheet of plane glass, fog, a piece of red hot iron, an umbrella, a lighted fluorescent tube, a wall, a sheet of carbon paper, the flame of a gas burner, a sheet of cardboard, a lighted torch, a sheet of cellophane, a wire mesh, kerosene stove, sun, firefly, the moon)
Answer :
2. Can you think of creating a shape that would give a circular shadow if held in one way and a rectangular shadow if held in another way?
Answer: Yes, a cylinder can produce a circular shadow when held in one way and a rectangular shadow when held in another way.
3. In a completely dark room, if you hold up a mirror in front of you, will you see a reflection of yourself in the mirror?
Answer: No, because for the reflection to happen, light is very important. So, in a dark room, a mirror cannot cast reflection of the image
4. What are shadows?
Answer: A shadow is a dark area formed on a surface when ligh passes against an opaque object. An opaque object blocks light from a light source resulting in forming a real image at the background.
5. Is it possible to produce a shadow through a glass?
Answer: No, because glass is a transparent object. Shadow is formed when an opaque object blocks the passage of light from one side to another.
6. Name the instrument used to split white light into 7 colors.
Answer: A prism is used to split white light into seven colors.
7. What is a luminous object? Give examples.
Answer:The objects which emit light on their own are called luminous bodies, e.g., the sun, the stars, etc.
8.Can you say that moon is a luminous body?
Answer: No, because moon can reflect the light from the sun but it cannot produce light on it’s own
9. Why do the Sun and Moon appear blurry when seen through clouds?
Answer: Clouds are translucent, All translucent objects allow partial light to pass through, making objects appear blurry. Hence, we can see blurry sun and moon through the clouds.
10. List some natural and artificial sources of light.
Answer: Natural sources of light are, sun, stars and fire. Some artificial sources of light are candles, lanterns, lamps, torches, and bulbs.
11. Mention the requirements for casting a shadow?
Answer: We need a source of light, an opaque object blocking the light, and a screen to receive the shadow.
12. How does light travel?
Answer: Light travels in a straight line
13. What is the colour of sunlight?
Answer : Sunlight appears white, but it is a combination of seven colors (VIBGYOR: Violet, Indigo, Blue, Green, Yellow, Orange, and Red). Violet, indigo, blue, green, yellow, orange and red
14. Can you give one example of natural event to prove that sunlight has 7 colors.
Answer: A rainbow appears after rain due to the dispersion of sunlight into its seven colors.
15. What is a pinhole camera?
Answer:It is a device used to obtain a photograph like image of a bright object on a screen.
16. The image formed in a pinhole camera is inverted, explain.
Answer:In a pinhole camera, the image is inverted because light travels in straight lines and crosses over through the pinhole.
17. Define reflection.
Answer:Reflection occurs when light bounces back to the medium from which it originated. To get the reflection, the light should hit a smooth and shiny surface. Best example of a reflector is the mirror
18. Mirrors are best reflectors, explain.
Answer: Mirrors are perfect reflectors because they do not allow light to pass through them.
19. What are the 2 types of mirrors?
Answer: Concave and convex mirrors
20. Explain the scattering of light with the help of a simple experiment.
Answer: Fix a comb vertically and shine a torchlight through its bristles. Place another comb in front of the first one, and you will observe the light scattering, creating patterns.
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