Practice MCQ Questions and answers on Physics-GK

31

Which one of the following instruments is used to study dispersion of light ?

A) Microscope B) Telescope C) Spectrometer D) Photometer

Discuss

Answer & Solution

Answer: Option C

Solution:

Dispersion occurs when different frequencies of light have different phase velocities, due either to material properties (material dispersion) or to the geometry of an optical waveguide (waveguide dispersion). A spectrometer (spectro-photometer, spectrograph or spectroscope) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials. The variable measured is most often the light’s intensity but could also, for instance, be the polarization state.

32

Which one of the following is responsible for the working of Newton's colour disc experiment ?

A) Formation of pure spectra B) Formation of impure spectra C) Persistence of vision D) Principle of complementary colour

Discuss

Answer & Solution

Answer: Option C

Solution:

A Newton Disc can be created by painting a disc with the seven different colours. A combination of red, green and blue in the circular disc will yield the same result. This is due to the phenomenon called persistence of vision.

33

An object which absorbs all colours and reflects none appears:

A) White B) Grey C) Blue D) Black

Discuss

Answer & Solution

Answer: Option D

Solution:

A black object absorbs all wavelengths of light and reflects none and that's why it appears black. Consequently, black absorbs the most heat.

34

Microphone is a device which transforms the

A) Sound signal into current signal B) Current signal into sound signal C) Sound signal into light signal D) Light signal into sound signal

Discuss

Answer & Solution

Answer: Option A

Solution:

Microphone is a device which transforms the sound signal into current signal.

35

Conversion of heat into electrical energy is achieved by using :

A) Ammeter B) Hydrometer C) Voltmeter D) Thermocouple

Discuss

Answer & Solution

Answer: Option D

Solution:

Conversion of heat into electrical energy is achieved by using thermocouple.

36

How much calorie of energy is released by a boiled egg ?

A) 40 B) 50 C) 60 D) 77

Discuss

Answer & Solution

Answer: Option D

Solution:

77-78 calories are released in a large size boiled egg.

37

A stone is dropped from the roof of a house towards the ground. The kinetic energy of the stone will be maximum:

A) Just after it is dropped B) When it is just on the half-way C) Just before it touches the ground D) When it touches the ground

Discuss

Answer & Solution

Answer: Option C

Solution:

When an object reaches the ground it has its maximum value of kinetic energy just before touching the ground. Since kinetic energy + potential energy= Constant; so on reaching ground the potential energy of an object becomes zero (0). The kinetic energy on reaching ground becomes maximum.

38

A 4 kg object is moving horizontally with a speed of 5 m/s. To increase its speed to 10 m/s, the amount of net work required to be done on this object is:

A) 150 J B) 100 J C) 50 J D) 75 J

Discuss

Answer & Solution

Answer: Option A

Solution:

m=4 kg
u=5 m/s
v=10 m/s
according to work energy theorem
w=1/2*m*(v²-u²)
w=1/2*4*(10²-5²)
w=1/2*4*(100-25)
w=2×75
w=150 J

39

Gasoline is useful in cars because it has

A) Chemical potential energy B) Electrical potential energy C) Gravitational potential energy D) Kinetic energy

Discuss

Answer & Solution

Answer: Option A

Solution:

Gasoline is a colorless petroleum-derived flammable liquid that is used primarily as a fuel in spark-ignited internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. It is also called as Petrol. It has chemical potential energy, in combustion it is turned into light, sound, heat and kinetic energy.

40

Electric Motor converts ________ energy to mechanical energy

A) Sound B) Mechanical C) Chemical D) Electrical

Discuss

Answer & Solution

Answer: Option D

Solution:

Electric Motor converts electrical energy to mechanical energy.