Physics MCQs
Topic Notes: Physics
MCQs and preparation resources for competitive exams, covering important concepts, past papers, and detailed explanations.
Plato
- Biography: Ancient Greek philosopher (427–347 BCE), student of Socrates and teacher of Aristotle, founder of the Academy in Athens.
- Important Ideas:
- Theory of Forms
- Philosopher-King
- Ideal State
1
Which type of electromagnetic wave is typically utilized by law enforcement radar guns to determine the velocity of an approaching vehicle?
Answer:
radio waves
Police radar guns operate by emitting radio waves toward a moving vehicle. The waves reflect off the vehicle and return to the radar unit. By measuring the frequency shift of the reflected waves (the Doppler effect), the device calculates the vehicle's speed. While microwaves are a subset of radio waves, 'radio waves' is the standard classification for this technology.
2
Under what conditions does the Doppler effect occur regarding a sound source?
Answer:
Both A & B
The Doppler effect is the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. It occurs whenever there is relative motion between the source and the observer. If the source moves towards the observer, the frequency increases; if it moves away, the frequency decreases.
3
Which of the following parameters does not influence the Doppler shift in the observed frequency of a wave?
Answer:
distance from the source to the listener
The Doppler effect describes the change in frequency due to the relative motion between a source and an observer. The shift depends on the source frequency and the relative velocities of the source and observer, but it is independent of the absolute distance between them.
4
How does the perceived frequency of a sound source change when it moves away from a stationary observer?
Answer:
Frequency appears to drop
According to the Doppler effect, when a sound source moves away from a stationary observer, the sound waves are stretched out in the direction of motion. This increase in wavelength results in a decrease in the frequency perceived by the observer, causing the sound to have a lower pitch.
5
The Doppler effect, which describes the change in frequency of a wave in relation to an observer moving relative to the wave source, is applicable to which types of waves?
Answer:
Both A and B
The Doppler effect is a general wave phenomenon. It occurs whenever a source of waves is in motion relative to an observer. This principle applies to mechanical waves, such as sound waves traveling through air, and electromagnetic waves, such as light waves traveling through a vacuum or medium, making both options A and B correct.
6
Which type of electromagnetic wave is typically utilized by police radar guns to measure the velocity of an approaching vehicle?
Answer:
radio waves
Police radar guns operate on the principle of the Doppler effect. They emit radio waves (often in the microwave frequency range) toward a moving vehicle. The waves reflect off the vehicle and return to the radar gun with a shifted frequency. By measuring this frequency shift, the device calculates the speed of the vehicle relative to the radar source.
7
How does the pitch of a train's whistle change for a stationary observer as the train approaches versus when it departs?
Answer:
of higher pitch when train arrives
This is an application of the Doppler Effect. As the train approaches, the sound waves are compressed, resulting in a higher observed frequency (pitch). As the train departs, the waves are stretched, resulting in a lower observed frequency.
8
Which physical principle is utilized to determine the velocity of a star relative to an observer on Earth?
Answer:
Doppler effect
The Doppler effect is the shift in the observed frequency of a wave due to the relative motion between the source and the observer. By measuring the redshift or blueshift of light emitted by stars, astronomers can calculate the radial velocity of the star relative to Earth, providing essential data for galactic motion studies.
9
Which physical phenomenon allows for the determination of a star's velocity relative to Earth?
Answer:
Doppler effect
The Doppler effect causes a shift in the observed frequency of light emitted by a star. If a star is moving away from Earth, the light is redshifted (frequency decreases), and if it is moving toward Earth, it is blueshifted (frequency increases). Astronomers use this shift to calculate the radial velocity of celestial objects.
10
How does the perceived pitch of a train whistle change as the train approaches versus when it departs from a stationary observer on a platform?
Answer:
Of higher pitch when train arrives
This phenomenon is known as the Doppler Effect. When a source of sound moves toward a stationary observer, the sound waves are compressed, resulting in a higher frequency and thus a higher pitch. Conversely, when the source moves away, the waves are stretched, resulting in a lower frequency and a lower pitch. The relative motion between the source and the observer dictates the shift in frequency observed.