Sound Wave Speed — 7 Physics PYQs with Answers | UKPSC PYQ Hub

Question 1

What will be the de Broglie wavelength of a ball of ms–1 mass 0.12 kg moving with a speed of 20 ?

Accepted Answer

2.76 × m. The de Broglie wavelength of an object is given by the formula: h λ = mv (6.63×10-34 where, h is plank's constant Js) m is the mass of the object (0.12kg) v is the velocity of the object (20m/s) Let's calculate the de Broglie wavelength

Question 2

63×10−34 λ= 0.12×20 6.63×10−34 λ = 2.4 10-34m λ = 2.76 × 36. Who among the following invented 'X-Rays'?

Accepted Answer

Roentgen. Roentgen invented X-Rays in 1895.

Question 3

A radar which ascertains the location and presence of Enemy's aircraft use–

Accepted Answer

Radio waves. RADAR stands for Radio Detecting And Ranging. It is based on the use of radio waves. Radars send out electromagnetic or radio waves. The signals are sent out as short pulses which may be reflected by objects in their path, in part reflecting back to the radar. When these pulses intercept precipitation, part of the energy is scattered back to the radar.

Question 4

The velocity of sound is maximum in

Accepted Answer

Metal. The velocity of sound is maximum in metal followed by liquid and gas. Sound cannot travel through vacuum.

Question 5

Which of the following is a mechanical wave?

Accepted Answer

Sound waves. Sound waves are characterized by the motion of particles in the medium and are called mechanical waves.

Question 6

Electrons may be emit ted from a metal surface if light falling on it has

Accepted Answer

small wavelength. Since we know that the formula µ= that λ is, if the frequency of light falling on a surface is high, then it will have minimum wavelength .

Question 7

Rays without charge are

Accepted Answer

X-rays. X-rays are charge less. It was discovered by Wilhelm Rontgen in the year 1895. It is a form of electromagnetic radiation.