Physics (Part-2) (CDS-Solved Paper)

Total Questions: 50

11. Light travels in a straight line (rectilinear propagation of light). This statement does hold, if the medium of travel for light is [Morning Shift-2017 (I)]

Correct Answer: (c) homogeneous and transparent
Solution:

Rectilinear propagation means that, light travels in a straight line. Formation of shadows and eclipses are the direct consequences of rectilinear propagation. In a homogeneous and transparent, medium light travels in a straight line and this is known as rectilinear propagation of light. Hence, option (c) is correct.

12. The spring constant of a spring depends on its [Morning Shift-2017 (I)]

Correct Answer: (d) thickness, its diameter and its material
Solution:

The spring constant of a spring depends on material of the spring. It also depends upon thickness, length as well as its diameter.
Hence, option (d) is correct.

13. The pressure exerted by a 760 mm column of mercury at 0°C is known as [Morning Shift-2017 (I)]

Correct Answer: (b) 1 atm
Solution:

The value of atmospheric pressure on the surface of earth at sea level, is called one atmosphere (1 atm) and is nearly equal to 1.013 × 10⁵ N/m². Atmospheric pressure is also called barometer pressure. One atm is the pressure exerted by a 760 mm column of mercury at 0°C.

14. Which one of the following statement(s) is/are not correct? [Morning Shift-2017 (I)]

Correct Answer: (b) The sensitivity of the human ear does not vary with the frequency of the sound.
Solution:

The sensitivity of the human ear depends upon the frequency of sound. It is most sensitive in the frequency range 20 Hz to 20000 Hz.
Hence, option (b) is correct.

15. In a bi-polar junction transistor, [Morning Shift-2017 (I)]

Correct Answer: (d) the base has the least concentration of impurity
Solution:

A junction transistor is three-terminal semiconductor device consisting of two p-n junctions formed by placing a thin layer of doped semiconductor (p-type or n-type) between two thick similar layers of opposite type. A transistor has three doped regions forming two p-n junctions between them. Hence, in a bi-polar junction transistor, the base has the least concentration of impurity.

16. The rate of change of momentum of a body is equal to the resultant [Morning Shift-2016 (I)]

Correct Answer: (c) force
Solution:

17. The SI unit of mechanical energy is [Morning Shift-2016 (I)]

Correct Answer: (a) joule
Solution:

The sum of kinetic energy and potential energy is called mechanical energy,
i.e. ME = KE + PE
So, SI unit of mechanical energy is joule.

18. Two systems are said to be in thermal equilibrium, if and only if [Morning Shift-2016 (I)]

Correct Answer: (c) there is no heat flow between them
Solution:

Two systems are said to be in thermal equilibrium, if there is no flow of heat between them when they are brought into thermal contact. If there is a temperature difference between them, then the flow of heat will be there, till it reaches to the same temperature. Hence, option (c) is correct.

19. Which one of the following statements is correct? The velocity of sound [Morning Shift-2016 (I)]

Correct Answer: (d) is maximum in solids and minimum in gases
Solution:

The velocity of sound depends upon the nature of medium. The speeds of sound in air, water and steel at 0°C are
Therefore, velocity of sound is maximum in solids and minimum in gases.

20. Which one of the following statements is not correct? [Morning Shift-2016 (I)]

Correct Answer: (b) Sound waves having frequency below 20 Hz are known as ultrasonic waves.
Solution:

Sound waves of frequency less than 20 Hz is known as infrasonic sound or infrasound. Sound waves of frequency greater than 20 kHz is known as ultrasonic sound or ultrasound. Sound waves are longitudinal waves. Higher amplitude sound waves are louder, whereas high frequency sound waves are sharp.