91.

Which one of the following statements is not correct?

• Ultrasonic waves cannot get reflected, refracted or absorbed.

• Ultrasonic waves are used to detect the presence of defects like cracks, porosity, etc. in the internal structure of common structure materials.

• Ultrasonic waves can be used for making holes in very hard materials like diamond.

• Ultrasonic waves cannot travel through vacuum.

Which one of the following devices changes low voltage alternating current to high voltage alternating current and vice-versa?

• Generator

• Motor

• Transformer

• Vibrator

An optical illusion which occurs mainly in deserts during hot summer is based on the principle of

• Reflection

• Interference

• Dispersion

• Total internal reflection

At which place Earth's magnetic field becomes horizontal?

• Magnetic meridian

• Magnetic equator

• Geographical pole

• Tropic of Cancer

The speed of a car travelling on a straight road is listed below at successive intervals of 1s:

0 1 2 3 4 Time (s)
0 2 4 6 8 Speed (m/s)

Which of the following is/are correct?

The car travels
1. with a uniform acceleration of 2 m/s²
2. 16m in 4s
3. with an average speed of 4 m/s.

Select the correct answer using the code given below:

• 1, 2 and 3

• 2 and 3 only

• 1 and 2 only

• 1 only

The speed of a body that has Mach number more than 1 is

• supersonic

• subsonic

• 300 m/s

• about 10 m/s

Which one ofthe following statements is NOT correct?

• In the conduction mode of transference of heat, the molecules of solid pass heat from one molecule to another without moving from their positions.

• The amount of heat required to raise the temperature of a substance is called its specific heat capacity.

• The process of heat transfer in liquids and gases is through convection mode.

• The process of heat transfer from a body at higher temperature to a body at lower temperature without heating the space between them is known as radiation.

The amount of heat required to change a liquid to gaseous state without any change in temperature is known as

• specific heat capacity

• mechanical equivalent of heat

• latent heat of vaporization

• quenching

The following figure shows displacement versus time curve for a particle executing simple harmonic motion:

Which one of the following statements is correct?

• Phase of the oscillating particle is same at t = 1s and t = 3s

• Phase of the oscillating particle is same at t = 2s and t = 8s

• Phase of the oscillating particle is same at t = 3s and t = 7s

• Phase of the oscillating particle is same at t = 4s and t = 10s

Match List-I with List-II and select the correct answer using the codes given below the Lists:

List I (Disease): (a) Hypermetropia, (b) Presbyopis, (c) Mopia, (d) Cataract

List II (Remedy): (1) Concave lens, (2) Bifocal lens, (3) Surgery, (4) Convex lens

• (a) - 4, (b) - 2, (c) - 1, (d) - 3

• (a) - 4, (b) - 1, (c) - 2, (d) - 3

• (a) - 3, (b) - 1, (c) - 2, (d) - 4

• (a) - 3, (b) - 2, (c) - 1, (d) - 4