West Bengal Board Solutions for Chapter: Physical Environment, Exercise 18: Exercise 18

Observe the following experiment and answer the following question.

Your teacher has put on the laser torch and has held it towards the wall. A spot of light has been cast on the wall. Since your teacher has held the torch, the spot of light is shimmering on the wall. So the torch has to be placed on a table. Now the torch has come to rest. As a result of it, the light spot has also come to rest. Mark the light spot as A on the wall where it has been cast. After that, the glass block or the paperweight is placed in the path of the laser beam. Now the laser beam has passed through the glass and has fallen on the wall. Look at the wall and see whether the light spot is cast at A on the wall or not.

Now think why the light spot has changed its position. Has the light changed its path? Why does it do so? Think about it.

Observe the following experiment and answer the following question.

Your teacher has put on the laser torch and has held it towards the wall. A spot of light has been cast on the wall. Since your teacher has held the torch, the spot of light is shimmering on the wall. So the torch has to be placed on a table. Now the torch has come to rest. As a result of it, the light spot has also come to rest. Mark the light spot as A on the wall where it has been cast. After that, the glass block or the paperweight is placed in the path of the laser beam. Now the laser beam has passed through the glass and has fallen on the wall. Look at the wall and see whether the light spot is cast at A on the wall or not.

Now remove the glass block or the paperweight. What do you observe now? Does the light spot come back to its initial position? Is the glass blocks or the paperweight responsible for the above incident.