Light, Shadows and Reflections

Q22. What exactly are shadows?

Ans. The dark area formed behind the opaque object, when the light from light source is blocked by it is called shadow.

Q23. What do we see when we look into the mirror?

Ans. We see reflection of our face in the mirror. We also see reflections of other objects that are in front of the mirror.

Q24. What advantage the pinhole camera has over the more usual lens camera?

Ans. One advantage the pinhole camera has over the more usual lens camera is that it does not need to be focused.

Q25. What do you understand by scattering of light?

Ans. When a beam of light falls on rough surface, it bounces back in different directions. This is called scattering of light.

Q26. Why train and airplane services are disturbed on rainy or foggy day?

Ans. Train and airplane services are disturbed on rainy or foggy day because air becomes translucent and visibility reduces.

Q27. Can we see our reflection in a mirror in a completely dark room?

Ans. No, because there is no source of light .We can see our image only when light is reflected from the mirror.

Q28. What is lateral inversion?

Ans. In lateral inversion the right side of the object appears to be the left side of its image and vice-versa.

Q29. What is reflection of light?

Ans. When the light rays strike the smooth or shiny area, it bounces back to the same medium. This phenomenon is called reflection of light.

Q30. Write some man-made or artificial sources of light.

Ans. Some man-made sources of light are candles, oil lamps, earthen lamps, lanterns, gas lamps, electric bulbs, tube light, fluorescent tubes etc.

Q31. Why it is not possible to see the candle flame from a bent pipe?

Ans. It is not possible to see the candle flame from a bent pipe because light cannot pass through the bent pipe.

Q32. What are the characteristic of the image formed by plane mirrors?

Ans. Images formed by plane mirrors are virtual, upright, left-right reversed, the same distance from the mirror as the object's distance, and the same size as the object.

Q33. How is the shadow of an object affected by its distance from a light?

Ans. When object moves closer to the source of light, the shadow becomes larger and when object moves away from the source of light, the shadow becomes smaller.

Q34. Does cloud transmit light?

Ans. Yes, as they are made up of vapor they can transmit light as well as reflect it. That is why sometimes we are able to see sun or moon behind the clouds.

Q35. How can you convert a transparent glass sheet into a translucent glass sheet?

Ans. We can convert a transparent glass sheet into a translucent glass sheet in the following ways:

                      i.        By covering one side of the sheet with butter paper.

                     ii.        By applying oil on one side of the sheet.

Q36. Why are the moon and the planets considered as non-luminous objects?

Ans. The moon and the planets are considered as non-luminous objects because they do not produce light of their own. Instead they reflect light from the sun falling on them.

Q37. Why light is essential to sustain life of human beings, animals and plants?

Ans. Oxygen is essential for us to live, is produced by plants in the presence of sunlight. Plants cannot prepare their food in the absence of light. Both we and animal get food from plants.