Question
Sound can make a light spot dance. Describe a simple experiment to illustrate this fact.
Solution
Experiment to show that sound can make a light spot dance.
Fig. 12.7. A beam of light from a light source is made to fall on a mirror. The reflected light is falling on the wall.
i) Take a tin can. Remove both ends to make it a hollow cylinder.
Fig. 12.7. A beam of light from a light source is made to fall on a mirror. The reflected light is falling on the wall.
i) Take a tin can. Remove both ends to make it a hollow cylinder.
ii) Take a balloon and stretch it over the can, then wrap a rubber band around the balloon.
iii) Now, take a small piece of mirror. Stick the piece of mirror to balloon using a glue stick.
iv) Allow the light to fall on the mirror through the slit. After reflection, we can see the light spot on the wall as seen in the fig.
v) Shout directly into the open end of the can and observe the dancing light spot on the wall.
vi) The sound wave incident on the back of the mirror makes set it into vibration. As a result, the reflected spot of light appears to dance on the wall.
iii) Now, take a small piece of mirror. Stick the piece of mirror to balloon using a glue stick.
iv) Allow the light to fall on the mirror through the slit. After reflection, we can see the light spot on the wall as seen in the fig.
v) Shout directly into the open end of the can and observe the dancing light spot on the wall.
vi) The sound wave incident on the back of the mirror makes set it into vibration. As a result, the reflected spot of light appears to dance on the wall.
