Light Chapter 9 Class 4 (Frank Bro's & Co.)

 I. Short Answer Questions

1. What type of object forms clear, dark shadows?

Ans:  Opaque object.

2. What happens when light passes through a prism?

Ans: When light passes through a prism, it bends and splits into seven colors, forming a rainbow-like spectrum.

3. Why does an arrow change direction when viewed through a glass full of water?

Ans: The arrow looks reversed because of the bending of light, called refraction, when it passes through water and glass.

4. What type of glass is best suited to make night lamps?

Ans: Translucent glass is best because it allows light to pass through softly without being too bright.

5. Give an example of reflection of light in our daily life.

Ans: Seeing yourself in a mirror is an example of reflection of light.

II. Long Answer Questions:

1. Why is the Sun the most important source of light on Earth?

Ans: The Sun gives us light and heat, which are necessary for life. It helps plants grow by giving them energy to make food. It also keeps our planet warm and gives us daylight. Without the Sun, Earth would be dark, cold, and lifeless.

2. What are non-luminous objects? Give examples.

Ans: Non-luminous objects are things that do not give off their own light. We can see them only when light shines on them from another source. For example, a table, a book, and a pencil are non-luminous because they don’t glow by themselves.

3. How can we show that light travels in a straight line?

Ans: Take three pieces of cardboard and make a small hole in each. Stand them up in a straight line. Place a burning candle on one end and look through the holes from the other side. If the holes are in a straight line, you can see the candle. If one cardboard is moved, the light is blocked. This shows light travels in a straight line.

4. What are transparent objects? Give examples.

Ans: Transparent objects let light pass through them completely. You can clearly see through them. These objects do not form shadows. Examples are clear glass, clean water, and clear plastic.

5. What affects the shadow’s darkness, size, and shape?

Ans: The shadow's darkness depends on how much light is blocked. Opaque objects make dark shadows. The size of the shadow changes with the distance between the object and the light source—closer objects make bigger shadows. The shape of the shadow depends on the shape of the object.