Physics MCQs
Physics Objective (Multiple Choice) General Knowledge & General Science Questions & Answers for SSC-CGL, UPPSC, NDA, CDS and all one day examinations of India.
41. Water is not suitable as a calorimetric substance because it :
[A] has high specific heat
[B] is a good conductor
[C] has high boiling point
[D] low latent heat of vapourization
Show Answer
Correct Answer: A [has high specific heat]
Notes:
The specific heat of water is higher than all other common substances. Hence, water is used for heating purposes (as in hot water bottles) and for cooling purposes (as in radiators of cars). Off all the liquids, mercury has the lowest specific heat due to which it is used as a thermometric liquid .
42. Quality of a musical note depends on
[A] Fundamental frequency
[B] Amplitude of the wave
[C] Harmonics present
[D] Velocity of sound in the medium
Show Answer
Correct Answer: C [Harmonics present]
Notes:
Sound “quality” or “timbre” describes those characteristics of sound which allow the ear to distinguish sounds which have the same pitch and loudness produced by different sources such as sitar and guitar, drum or dholak etc. Timbre is mainly determined by the harmonic content of a sound and the dynamic characteristics of the sound such as vibrator and the attack-decay envelope of the sound. Harmonic content is the most important of these.
43. The working principle of a mercury thermometer is__:
[A] Change in density of matter on heating
[B] Expansion of matter on heating
[C] Thermal resistance of matter
[D] Change in mass of matter on heating
Show Answer
Correct Answer: B [Expansion of matter on heating]
Notes:
Mercury thermometers are based on the principle that liquids expand when heated and contract when cooled. So, when the temperature increases, the mercury expands and rises up the tube and when the temperature decreases it contracts and does the opposite.
44. Which of the following colour of light deviates least through the prism?
[A] yellow
[B] green
[C] violet
[D] red
Show Answer
Correct Answer: D [red]
Notes:
In refracting media like glass prism, water, etc. , lights of different colors travel with different speeds because of their different wavelengths Cc= f N. The speed of violet colour is the least, while the speed of red colour is the largest in prism. As a result, the refractive index of glass is largest for violet colour and least for red colour. So, the violet colour is deviated the most, while red colour is deviated the least when passing through the prism.
45. In a filament type light bulb, most of the electric power consumed appears as__:
[A] visible light
[B] infra-red rays
[C] ultra-violet rays
[D] fluorescent light
Show Answer
Correct Answer: B [infra-red rays]
Notes:
When electricity is passed through the tungsten filament, the filament gets hot. Depending on the temperature of the filament, radiation is emitted from the filament. The filament temperature is very high, generally over 2,000°C. At this high temperature of 2,000°C, about 5 percent of the electrical energy converts into visible light and rest of it is emitted as heat (infrared radiation).
46. Which of these waves can be polarized__?
[A] Sound waves in air
[B] Longitudinal waves on a string
[C] Transverse waves on a string
[D] Light waves
Show Answer
Correct Answer: D [Light waves]
Notes:
It is possible to transform unpolarized light into polarized light. A light wave that is vibrating in more than one plane is referred to as unpolarized light. Polarized light waves are light waves in which the vibrations occur in a single plane. The process of transforming unpolarized light into polarized light is known as polarization.
47. Siemens is aunit of which of the following?
[A] Magnetic flux density
[B] Electrical conductance
[C] Magnetic flux
[D] Capacitance
Show Answer
Correct Answer: A [Magnetic flux density]
Notes:
Incandescent light bulbs consist of an air-tight glass enclosure with a filament of tungsten wire inside the bulb, through which an electric current is passed. Tungsten is used because it has the highest melting point (>3400 degrees C) of any metal.
48. According to special theory of relativity the mass of a particle
[A] increases with increase in velocity with respect to an observer.
[B] decreases with increase in velocity.
[C] decreases with decrease in velocity.
[D] is independent of its velocity.
Show Answer
Correct Answer: A [increases with increase in velocity with respect to an observer.]
Notes:
According to the Special Theory of Relativity, the mass of a moving object measures more as its velocity increases until, at the speed of light, it becomes infinite. This is because as an object gains speed, it gains more (kinetic) energy.
49. Which of the following are the highest-frequency electro magnetic waves?
[A] Gamma Rays
[B] Radio Waves
[C] Ultraviolet Rays
[D] Microwaves
Show Answer
Correct Answer: A [Gamma Rays]
Notes:
Gamma rays are the highest energy electromagnetic radiation and typically have energies greater than 100 keV, frequencies greater than 1019 Hz, and wavelengths less than 10 picometers. They are typically produced from the decay of atomic nuclei. The most powerful sources of gamma-rays are caused by astronomical events.
50. Which device is used for measuring the wavelength of X-rays?
[A] G.M. Counter
[B] Cyclotron
[C] Bragg Spectrometer
[D] Mass Spectrometer
Show Answer
Correct Answer: C [Bragg Spectrometer]
Notes:
Bragg Spectrometer is an instrument used to analyze crystal structure by using X-rays. In it, a beam of collimated X-rays strikes the crystal, and a detector measures the angles and intensities of the reflected beam.
