Physics: Optics, Waves, and Acoustics
Test on light and sound phenomena including mirrors, refraction, total internal reflection, wave properties, and sound velocity
Questions
Which of the following statements related to the image formed by a plane mirror is correct?
- A plane mirror always forms a real image.
- The image formed by a plane mirror may be magnified or diminished.
- The image formed by a plane mirror is always unmagnified and inverted.
- The image formed by a plane mirror is always unmagnified and erect.
A completely transparent material will be invisible in vacuum when the refractive index is
- unity
- more than unity
- less than unity
- equal to 1.33
Total internal reflection of light can occur only when light passes
- from a denser to a rarer medium
- from a rarer to a denser medium
- from one medium to another of equal refractive index
- from one medium to another of equal absorption
Critical angle of light passing from glass to air is the minimum for which colour?
- Red
- Green
- Yellow
- Violet
Which of the following statements about light rays is incorrect?
- Light always propagates along a straight line.
- Two light rays do not disturb each other upon intersection.
- An object and its image are interchangeable.
- None of these
One cannot see through fog because
- fog absorbs light
- light is scattered by the droplets in the fog
- light suffers total reflection in the droplets in the fog
- the refractive index of fog is infinity
Two plane mirrors are inclined at an angle of 72o, and a point object is placed between the two mirrors. The number of images formed is
- 3
- 4
- 5
- 6
The velocity of sound in any gas depends upon
- the wavelength of sound only
- the density and elasticity of the gas
- the intensity of sound waves only
- the amplitude and frequency of sound
When two or more notes which produce concord are sounded simultaneously, the pleasing effect produced is called
- harmony
- melody
- chord
- musical interval
A person of height h is standing at the centre of the room looking towards a plane mirror hung on a wall. He can see the whole height of the wall behind him if the length of the mirror is
- h
- h/2
- h/3
- h/4
The ratio of refractive index of red light to that of blue light is
- less than unity
- equal to unity
- greater than unity
- less as well as greater than unity, depending upon the experimental arrangements
The refractive index of a given piece of transparent quartz is the greatest for
- red light
- violet light
- green light
- yellow light
In a doctor's stethoscope, the sound is intensified because of
- resonance of sound
- constructive interference
- principle of superposition of waves
- reflection of sound
Which of the following statements related to the laws of reflection is incorrect?
- The reflected ray and the incident ray lie in the same plane.
- The incident ray, reflected ray and the normal ray are concurrent.
- The angle of incidence is equal to the angle of reflection.
- None of these
Which of the following statements is/are TRUE?
- A "real object" always produces a "virtual image" in a plane mirror. This is because the reflected rays diverge.
- A ray parallel to the principal axis, after reflection, will pass through the centre of curvature in case of a concave mirror.
- Concave mirrors are commonly used as rear-view (wing) mirrors in vehicles.
- All of the above
Energy is not carried by
- transverse progressive wave
- longitudinal progressive wave
- stationary wave
- electromagnetic wave
In stationary waves,
- energy is uniformly distributed
- energy is maximum at nodes and minimum at antinodes
- energy is minimum at nodes and maximum at antinodes
- alternating maxima and minima of energy are produced at nodes and antinodes
Assertion (A): The velocity of sound in air increases due to the presence of moisture in it.
Reason (R): The presence of moisture in air lowers the density of air.
- Both (A) and (R) are true and (R) is the correct explanation of (A).
- Both (A) and (R) are true, but (R) is not the correct explanation of (A).
- (A) is true, but (R) is false.
- (A) is false, but (R) is true.
Who named charges as positive and negative charges?
- Faraday
- Gauss
- Benjamin Franklin
- Madam Curie
The refractive index of glass with respect to water is 9/8. It implies that
- the speed of light respectively is 9 times and 8 times slower in glass and water with respect to vacuum
- the speed of light in glass is 9/8 times faster than that in water
- <font size="2" face="Arial">the speed of light in water is 9/8 times faster than that in glass</font>
- None of these
Which of the following statements is wrong?
- Light travels faster in vacuum than in air.
- The wavelength of light is longer than the wavelength of sound.
- Light travels nearly 330 metres in one second.
- Speed of sound is mach one.
Which of the following statements related to the properties of images formed by a plane mirror is/are correct?
- The image has left-right reversal.
- The image has front-back reversal.
- The image has no top-bottom reversal.
- All of the above
Mirages are observed in the atmosphere due to the phenomenon of
- interference of light
- total internal reflection of light
- scattering of light
- double refraction of light
If a diver in a swimming pool wants to signal his distress to a person lying on the edge of the pool by flashing his waterproof flashlight, then
- he must direct the beam vertically upwards
- he has to direct the beam horizontally
- he has to direct the beam at an angle to the vertical, which is slightly less than the critical angle of incidence for total internal reflection
- he has to direct the beam at an angle to the vertical, which is slightly less than the critical angle
A missile is launched with a velocity less than the escape velocity. The aggregate of its potential energy and kinetic energy will be
- positive
- negative
- zero
- positive and negative