(a) One end of a plastic foot ruler is held tightly at the edge of a table and the other end is plucked. Name the vibrations produced in the ruler. (b) Now the ruler is pushed inside partially and plucked again from its free end. State with a reason whether the frequency of vibration increases or decreases.

The displacement–time graph of a sound wave produced by a vibrating wire is shown below. (a) How will you adjust the tension in the wire, to reduce the length of PR? (b) Which characteristic of sound is affected by the reduction in the length of PR?

A metal foot ruler is held at the edge of a table. It is pressed at its free end and then released. It vibrates. (a) Name the vibrations produced. (b) State one way to increase the frequency of these vibrations.

Rohan conducted experiments on echo in different media. He observed that a minimum distance of ‘x’ meters is required for the echo to be heard in oxygen and ‘y’ meters in benzene. Compare ‘x’ and ‘y’. Justify your answer. Speed of sound in oxygen: 340 ms-1 Speed of sound in benzene: 200 ms-1

(a) Which characteristic of sound is affected due to the larger surface of a school bell? (b) Calculate the distance covered by the Ultrasonic wave having a velocity of 1.5 km s⁻¹ in 14 s, when it is received after reflection by the receiver of the SONAR.

When the stem of a vibrating tuning fork is pressed on a table, the tabletop starts vibrating. These vibrations are definitely an example of: (a) resonance (b) natural vibrations (c) forced vibrations (d) damped vibrations

We are able to see the T.V. channels clearly when we set T.V. on auto-tuning. (a) Which phenomenon led to the clear visibility of the channels, due to auto tuning? (b) Define the above phenomenon mentioned by you. (c) Give any one more example of this phenomenon.

Two notes are produced from two different musical instruments, such that they have same loudness and same pitch. The produced notes differ in their: (a) Waveform (b) Frequency (c) Wavelength (d) Speed

When a body vibrates under a periodic force, the vibrations of the body are always: (a) natural vibrations (b) damped vibrations (c) forced vibrations (d) resonant vibrations

The diagrams given below show two sound boxes A and B with wires of the same length (l) and tension (10 kgf) but different cross-sectional areas. Simultaneously, vibrating tuning forks of frequency 300 Hz are placed on boxes A and B. The paper rider falls off in case of B but not in case of A. (a) Name and explain the phenomenon responsible for the falling off of the paper rider in B. (b) The wire A resonates with a tuning fork of frequency ‘f’. Is ‘f’ greater than, less than or equal to 300 Hz? Justify your answer.

A submarine in the sea, sends an ultrasonic ping and a stopwatch is started simultaneously. The stopwatch stops on receiving the reflected wave from an obstacle and reads 1 minute 40 seconds. Calculate the distance of the obstacle from the submarine. (Speed of sound in water = 1500 m s⁻¹)

Assertion (A) : As the level of water in a tall measuring cylinder kept under running tap rises, the pitch of sound gradually increases. Reason (R) : Frequency of sound is inversely proportional to the length of the water column. (a) Both (A) and (R) are true and (R) is correct explanation of (A). (b) Both (A) and (R) are true and (R) is not the correct explanation of (A). (c) (A) is true but (R) is false. (d) (A) is false but (R) is true.