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6th Class (CBSE) Science: Light, Shadows and Reflections

6th Class (CBSE) Science: Light, Shadows and Reflections

Question: We see the sun rising 81/4 minutes after it has actually risen. Why?

Answer: The distance from the sun to the earth is 1485 lakh Kilometers. We can calculate that light travels from the sun to the earth in 81/4 minutes. That means we see the sun rising 81/4 minutes after it has risen.

Question: Name two natural sources of light and two human-made sources of light.

Answer: Man made sources of light are – tube light and candle. Natural sources of light are – sun and firefly

Question: How do we see non-luminous objects?

Answer: Objects that do not produce their own light are called non-luminous objects. We can see non-luminous objects when,

  1. light falls on non-luminous objects, such as book
  2. The object should reflect light towards our eyes.

Question: To see an object what do we need?

Answer:  To see any non-luminous object we need the following:

  1. Source of light
  2. an object
  3. eyes

When a light emitting from luminous body falls on a non-luminous object and is reflected. This reflected light reaches our eyes enables us to see that object.

Question: Moon appears bright at night. Is it a luminous or non-luminous body?

Answer: Moon is a non-luminous body, it does not emit its own light. It reflects the sun light that falls on it.

Question: What is meant by rectilinear propagation of light?

Answer: The light that travels in straight line is called rectilinear propagation of light. For example: When we shine a torch in the dark, light appears to go straight outwards. Similarly the light from the cinema projector also appears to take a straight path to the screen.

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