Question

How will you verify laws of reflection of sound experimentally?

Answer 1

Step 1: Laws of reflection

The reflection of sound obeys two types of laws:

Law 1: The angle of incidence is equal to the angle of reflection.

Law 2: The incidence wave, the reflected wave, and the normal lie in the same plane.

Step 2: Apparatus for the experiment

• A smooth polished large wooden board is taken and mounted vertically on a table.
• At the right angle to the board, a wooden screen is fixed.
• On each side of the screen, a long, narrow, and highly polished tube is placed from inside as shown in the figure.

Step 3: Procedure to verify the laws of reflection

• A watch is placed at the end of tube A.
• The tube B is moved slightly, left or right, till a distinct tick of the watch is heard.
• The ∠PCN and ∠RCN between the tubes and the normal is measured.
• ∠PCN represents an angle of incidence and ∠RCN represents the angle of reflection.
• It is found that ∠PCN = ∠RCN.
• Also the incidence wave, the reflected wave, and the normal lie in the same plane.
• Thus the experiment illustrates the laws of reflection.