Wave MCQ Quiz - Objective Question with Answer for Wave - Download Free PDF

The correct answer is Concave.

• Concave mirrors have reflecting surface curved inwards.
  • ​Concave mirrors reflect light inward to one focal point.
  • They are used to converge light.
  • Unlike convex mirrors, concave mirrors show different image types depending on the distance between the object and the mirror.

Additional Information

• A convex mirror is a curved mirror where the reflecting surface is oriented towards the light source.
• A concave mirror is a curved mirror where the reflecting surface is curved inward.
• A curved mirror is a mirror with a curved reflective surface.
  • The surface may be bent inward (concave mirror) or maybe raised outward (convex mirror).

The correct answer is Gamma Rays.

Key Points

• Gamma rays have the shortest wavelength and highest frequency (energy) in the electromagnetic spectrum.
• They are electromagnetic waves with wavelengths in the range of 10^-12m and frequencies around 10²⁰- 10²⁴ Hz.
• They have a high penetrating power.
• They are a result of decaying radioactive material and can also be found in outer space.
• They are used in medical applications for sterilisation of equipment and cancer treatment.

Additional Information

•  Other radiations in the Electromagnetic spectrum are:

The correct answer is remains same.

Concept:
Sound

• Sound is a form of energy which produces a sensation of hearing in our ears.
• Sound is produced by vibrating objects. The matter or substance through which sound is transmitted is called a medium. It can be solid, liquid or gas. 

Explanation:

• As the loudness of the mobile ringtone increases, the frequency of the ringtone remains same.
• The loudness is expressed in a unit called decibel (dB). 
• Loudness is the physical response of the ear to the intensity of sound.
• A sound with more energy is referred to as a strong sound.
• Loudness of sound is proportional to the square of the amplitude of the vibration producing the sound. 
• Loudness ∝ (amplitude)²
• The loudness of sound waves does not depend on the frequency of the sound waves. 
• Loudness and Amplitude: Loudness is the perception of how intense or strong a sound seems to our ears. It is directly related to the amplitude of a sound wave.
  • Increasing the amplitude increases the loudness, while decreasing the amplitude decreases the loudness.
• Frequency and Pitch: Frequency is the number of oscillations (cycles) that a sound wave completes in one second, measured in Hertz (Hz).
  • Pitch is the perceptual attribute of the sound that allows us to classify it as higher or lower; it is directly related to the frequency of the sound wave.
  • Higher frequency corresponds to a higher pitch, and lower frequency corresponds to a lower pitch.
• Intensity and Energy: Intensity is the amount of energy a sound wave carries per unit area per unit time, and it is proportional to the square of the amplitude.

Higher intensity results in louder sounds but does not affect the frequency.

Mistake Points

•  Loudness is related to amplitude.
• Pitch is related to frequency.
• Intensity is associated with energy of the sound wave and is proportional to amplitude squared.

Additional Information

• When the amplitude is greater, the loudness of the sound is also higher. 
• When the amplitude is low, the sound produced will be dim.

CONCEPT:

• Wave: The disturbance that transfers energy from one place to another is called a wave.

There are mainly two types of waves:

1. Transverse waves: The wave in which the movement of the particles is at right angles to the motion of the energy is called a transverse wave. Light is an example of a transverse wave.
2. Longitudinal wave: The wave in which the movement of the particles is parallel to the motion of the energy is called a longitudinal wave. The sound wave is an example of a longitudinal wave.

EXPLANATION:

• Light-wave is a transverse wave because its components vibrate perpendicular to its direction of propagation. So option 1 is correct.

The correct answer is option 2.

Key Points

• Half-life (T₁/₂) = Time required for half of a radioactive substance to decay.
• Let’s break it down:
  • After 1 half-life (4 months) → 50% of the substance remains.
  • After 2 half-lives (8 months) →
    • Half of the remaining 50% decays
    • So only 25% remains
    • That means 75% (3/4) has decayed.
• Therefore, it takes 8 months to decay 3/4th of the substance. 

CONCEPT:

• Wave: The disturbance that transfers energy from one place to another is called a wave.

There are mainly two types of waves:

1. Transverse waves: The wave in which the movement of the particles is at right angles to the motion of the energy is called a transverse wave. Light is an example of a transverse wave.
2. Longitudinal wave: The wave in which the movement of the particles is parallel to the motion of the energy is called a longitudinal wave. The sound wave is an example of a longitudinal wave.

EXPLANATION:

• Light-wave is a transverse wave because its components vibrate perpendicular to its direction of propagation. So option 1 is correct.

The correct answer is Gamma Rays.

Key Points

• Gamma rays have the shortest wavelength and highest frequency (energy) in the electromagnetic spectrum.
• They are electromagnetic waves with wavelengths in the range of 10^-12m and frequencies around 10²⁰- 10²⁴ Hz.
• They have a high penetrating power.
• They are a result of decaying radioactive material and can also be found in outer space.
• They are used in medical applications for sterilisation of equipment and cancer treatment.

Additional Information

•  Other radiations in the Electromagnetic spectrum are:

The correct answer is 850 m.

Key Points

• Echo: If we shout or clap near a suitable reflecting object such as a tall building or a mountain, we will hear the same sound again a little later. This sound which we hear is called an echo.
• Echoes are heard due to the phenomenon of Reflection of sound waves.
• To hear the echo clearly, the reflecting object must be more than 17.2 m from the sound source for the echo to be heard by a person standing at the source.

Additional Information

Given,

Time taken to heard first echo (t₁) = 2 sec

Time taken to heard second echo (t₂) = 3 sec

Velocity of sound (v) = 340 m/s

Let d be the distance between two cliffs, x is the distance between the man and cliff 2, and (d - x) is the distance between the man and cliff 1.

The speed of sound is

$SpeedofSound\left(v\right)=\frac{Distance\left(d\right)}{Time\left(t\right)}$

The distance between the man and cliff 2 is 

⇒ 2x = v × t₁

$\Rightarrow x=\frac{v\times t_1}{2}$

$\Rightarrow x=\frac{340\times 2}{2}=340m$

The distance between the man and cliff 1 is 

⇒ 2(d - x) = v × t₂

$\Rightarrow \left(d-x\right)=\frac{v\times t_2}{2}$

$\Rightarrow \left(d-340\right)=\frac{340\times 3}{2}=510$

⇒ d = (510 + 340) m = 850 m

Hence the correct option is 850 m.

• The pitch of a sound primarily depends on its frequency. Higher the frequency, higher is the pitch.
• Loudness and spectrum are the other parameters on which the pitch of a sound depends.
• The number of oscillations per unit time gives the frequency of the sound wave.
• The wavelength of a sound wave is the distance between two consecutive compressions (C) or two consecutive rarefactions (R).
• The amplitude is the maximum disturbance in the medium on either side of the mean value. It determines the loudness or softness of the sound.
• The quality of sound that helps in differentiating the two different sounds, is termed as timbre.

The correct answer is remains same.

Concept:
Sound

• Sound is a form of energy which produces a sensation of hearing in our ears.
• Sound is produced by vibrating objects. The matter or substance through which sound is transmitted is called a medium. It can be solid, liquid or gas. 

Explanation:

• As the loudness of the mobile ringtone increases, the frequency of the ringtone remains same.
• The loudness is expressed in a unit called decibel (dB). 
• Loudness is the physical response of the ear to the intensity of sound.
• A sound with more energy is referred to as a strong sound.
• Loudness of sound is proportional to the square of the amplitude of the vibration producing the sound. 
• Loudness ∝ (amplitude)²
• The loudness of sound waves does not depend on the frequency of the sound waves. 
• Loudness and Amplitude: Loudness is the perception of how intense or strong a sound seems to our ears. It is directly related to the amplitude of a sound wave.
  • Increasing the amplitude increases the loudness, while decreasing the amplitude decreases the loudness.
• Frequency and Pitch: Frequency is the number of oscillations (cycles) that a sound wave completes in one second, measured in Hertz (Hz).
  • Pitch is the perceptual attribute of the sound that allows us to classify it as higher or lower; it is directly related to the frequency of the sound wave.
  • Higher frequency corresponds to a higher pitch, and lower frequency corresponds to a lower pitch.
• Intensity and Energy: Intensity is the amount of energy a sound wave carries per unit area per unit time, and it is proportional to the square of the amplitude.

Higher intensity results in louder sounds but does not affect the frequency.

Mistake Points

•  Loudness is related to amplitude.
• Pitch is related to frequency.
• Intensity is associated with energy of the sound wave and is proportional to amplitude squared.

Additional Information

• When the amplitude is greater, the loudness of the sound is also higher. 
• When the amplitude is low, the sound produced will be dim.

CONCEPT:

• Sound: A local disturbance whose propagation is facilitated by the collisions between particles this disturbance propagates in a longitudinal wave, imagine one molecule hitting the next molecule, and then that molecule hitting the next, and so forth.
  • It is a mechanical wave that needs a medium to travel.
  • The speed of sound is maximum in solid then it is in liquid and slowest in gases.
  • Speed of sound: The distance traveled per unit time by sound waves as it propagates through an elastic medium.

The velocity of sound  in a gaseous medium is given by:

$\Rightarrow v=\sqrt{\frac{\gamma P}{\rho }}$

Where P = pressure, ρ = density, and γ = ratio of two principal specific heats of the gas

• The speed of sound remains almost the same for all frequencies in a given medium under the same physical conditions.
• A state of matter is one of the distinct forms in which matter can exist.
  • The four fundamental states of matters are - solids, liquids, gases, and plasma.

EXPLANATION:

• Solid-state is one of the four fundamental states of matter, in which the constituent particles (ions, atoms, etc) are closely packed together.
• The speed of sound is maximum in solids and least in gases. So option 4 is correct.

EXTRA POINTS

https://ncert.nic.in/ncerts/l/iesc112.pdf

 CONCEPT:

• Echo: If we shout or clap near a suitable reflecting object such as a tall building or a mountain, we will hear the same sound again a little later. This sound which we hear is called an echo.
  • Echoes are heard due to the phenomenon of Reflection of sound waves.
  • To hear the echo clearly, the reflecting object must be more than 17.2 m from the sound source for the echo to be heard by a person standing at the source.

Calculation:

Given that,

The time taken by the echo to reach back to the source (t)= 6s.

Velocity of the sound (v) = 346 m/s.

Distance between person and cliff (d) = v x t_a

As sound travels back and forth to form an echo and hence time is twice.

Now dividing the time take by 2 we get actual time (T_a)= 6/2 ⇒ 3

Therefore, the distance from person to the cliff (d) = 346 x 3 ⇒ 1038 m.

The distance between the person and the cliff is 1038 meters.

The correct answer is Amplitude.

• Loudness means how loud or soft a sound seems to a listener.

Key Points 

• Loudness is related to amplitude and intensity is one of the most salient qualities of a sound which is a measure of the amount of energy in sound waves.
• The unit of intensity is the decibel (dB).

Additional Information

• Speed- The speed of sound is the distance traveled per unit of time by a sound wave when it propagates through an elastic medium.
• Wavelength- The wavelength of a sound is the distance between adjacent identical parts of a wave.
• Frequency- The number of vibrations counted per second is called frequency. The unit of frequency is called hertz (Hz).

Concept -

• The speed of light is dependent on the refractive index of the medium it is travelling in. 
• The higher the refractive index of the medium, the lower is the speed of light.
• Hence, the speed of light in a medium is inversely proportional to the refractive index of the medium in which it is travelling through. 
• The denser a medium is the more is its refractive index and thus, the lesser is the speed of light. 
• The speed of light is thus minimum in solids as they are denser and will be maximum in a vacuum as a vacuum is the least dense medium.
• Speed of light follows the following order (decreasing)  
  • Vacuum > Air > Liquid > Solids 

​​Explanation -

• In the given four options in the question - Air, Glass, Vaccum, and water, the densest medium is glass as it is solid so the speed of light will be minimum in it.
• The speed of light is maximum in a vacuum.
• The speed of light in decreasing order will be, (according to this question) -  
  • Vacuum > Air > Water > Glass 
• Vacuum is the least dense medium with no obstruction to the path of light. Its refractive index is equal to unity, hence, the speed of light is maximum in a vacuum.

So, the speed of light is maximum in a vacuum.

Important Points

• Light in air travels at a little lesser speed than in a vacuum.
• Vacuum being a medium completely free from any kind of obstruction towards the flow of light causes a higher speed than air, which has a refractive index of slightly greater than one.

Additional Information

• The speed of sound follows a reverse order when compared with the speed of light in different mediums. 
• The speed of sound is maximum in solids and minimum in gases.
• The speed of sound, in decreasing order here, will be, 
  • Solids > Liquids > Gases
  • Sound can not travel in a vacuum. 
• Whereas the speed of light is maximum in a vacuum and the minimum in solids. 

• Light can travel in a vacuum because the light is electromagnetic in nature which requires no medium as electric fields and magnetic fields constantly generate each other as the wave propagates.
• Sound waves require a medium to travel. The speed of sound is faster in solid materials, slower in liquids and slowest in gases.
• The speed of light in a vacuum is commonly given the symbol c. It is a universal constant that has the value c = 3 x 10⁸ m/second.