Waves & Optics MCQ & Objective Questions
Waves & Optics is a crucial topic in physics that plays a significant role in various school and competitive exams. Mastering this subject not only enhances your conceptual understanding but also boosts your confidence in tackling MCQs and objective questions. Regular practice with these important questions can lead to improved scores and better exam preparation.
What You Will Practise Here
Fundamental concepts of wave motion and properties of waves
Types of waves: transverse and longitudinal
Reflection and refraction of light, including Snell's law
Interference and diffraction patterns
Optical instruments and their applications
Key formulas related to wave speed, frequency, and wavelength
Real-life applications of optics in technology and nature
Exam Relevance
The topic of Waves & Optics is frequently featured in CBSE, State Boards, NEET, and JEE exams. Students can expect questions that assess their understanding of wave properties, light behavior, and practical applications. Common question patterns include numerical problems, conceptual MCQs, and diagram-based questions that require a clear grasp of the subject matter.
Common Mistakes Students Make
Confusing the characteristics of transverse and longitudinal waves
Misapplying Snell's law in refraction problems
Overlooking the significance of phase difference in interference
Ignoring the units of measurement in wave equations
Failing to interpret diagrams accurately in optics questions
FAQs
Question: What are the key formulas I should remember for Waves & Optics?Answer: Important formulas include wave speed (v = fλ), Snell's law (n1 sin θ1 = n2 sin θ2), and the lens formula (1/f = 1/v - 1/u).
Question: How can I improve my understanding of Waves & Optics?Answer: Regularly solving Waves & Optics MCQ questions and reviewing key concepts will greatly enhance your understanding and retention.
Start solving practice MCQs today to test your understanding and solidify your knowledge in Waves & Optics. Your success in exams is just a question away!
Q. A car moving at 30 m/s emits a sound of frequency 500 Hz. What frequency does an observer standing still hear as the car approaches?
A.
500 Hz
B.
550 Hz
C.
600 Hz
D.
650 Hz
Show solution
Solution
Using the Doppler effect formula, f' = f(v + vo) / (v - vs), where v = 340 m/s, vo = 0, vs = 30 m/s, f' = 500(340)/(340 - 30) = 500(340/310) ≈ 548 Hz.
Correct Answer:
C
— 600 Hz
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Q. A sound source is moving away from an observer. If the source emits a sound of frequency 400 Hz, what frequency does the observer hear?
A.
Less than 400 Hz
B.
Exactly 400 Hz
C.
More than 400 Hz
D.
Infinity
Show solution
Solution
As the source moves away, the frequency decreases, so the observer hears a frequency less than 400 Hz.
Correct Answer:
A
— Less than 400 Hz
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Q. If a sound source is moving away from a stationary observer, which of the following describes the observed frequency?
A.
Higher than the source frequency
B.
Lower than the source frequency
C.
Equal to the source frequency
D.
Variable depending on distance
Show solution
Solution
The observed frequency decreases as the source moves away, due to the Doppler effect.
Correct Answer:
B
— Lower than the source frequency
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Q. If a sound wave travels from air into water, how does its speed change?
A.
Increases
B.
Decreases
C.
Remains the same
D.
Becomes zero
Show solution
Solution
The speed of sound increases when it travels from air (approximately 343 m/s) into water (approximately 1482 m/s).
Correct Answer:
A
— Increases
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Q. If a source of sound is moving towards a stationary observer, what happens to the frequency of the sound heard by the observer?
A.
It decreases
B.
It remains the same
C.
It increases
D.
It becomes zero
Show solution
Solution
According to the Doppler effect, if the source is moving towards the observer, the frequency increases.
Correct Answer:
C
— It increases
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Q. If light travels from air (n=1) into water (n=1.33), what happens to its speed?
A.
It increases
B.
It decreases
C.
It remains the same
D.
It doubles
Show solution
Solution
The speed of light decreases when it enters a medium with a higher refractive index.
Correct Answer:
B
— It decreases
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Q. In a polarizer, what happens to unpolarized light?
A.
It is completely absorbed
B.
It becomes polarized
C.
It is reflected
D.
It is refracted
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Solution
When unpolarized light passes through a polarizer, it becomes polarized, with the electric field oscillating in a specific direction.
Correct Answer:
B
— It becomes polarized
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Q. In a simple harmonic motion (SHM), what is the relationship between the period and frequency?
A.
T = f^2
B.
T = 1/f
C.
T = f
D.
T = 2πf
Show solution
Solution
The period (T) is the reciprocal of frequency (f), given by T = 1/f.
Correct Answer:
B
— T = 1/f
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Q. In simple harmonic motion, what is the relationship between the displacement and the restoring force?
A.
Directly proportional
B.
Inversely proportional
C.
Independent
D.
Constant
Show solution
Solution
In simple harmonic motion, the restoring force is directly proportional to the displacement and acts in the opposite direction.
Correct Answer:
A
— Directly proportional
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Q. In the Doppler effect, what happens to the frequency of a sound wave as the source moves towards the observer?
A.
It decreases
B.
It remains the same
C.
It increases
D.
It becomes zero
Show solution
Solution
As the source moves towards the observer, the waves are compressed, leading to an increase in frequency.
Correct Answer:
C
— It increases
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Q. In which situation does light undergo total internal reflection?
A.
When it passes from air to water
B.
When it passes from water to air at an angle greater than the critical angle
C.
When it passes from glass to air at any angle
D.
When it passes from air to glass
Show solution
Solution
Total internal reflection occurs when light travels from a denser medium to a less dense medium at an angle greater than the critical angle.
Correct Answer:
B
— When it passes from water to air at an angle greater than the critical angle
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Q. In which situation does total internal reflection occur?
A.
When light travels from a denser to a rarer medium
B.
When light travels from a rarer to a denser medium
C.
When light is absorbed
D.
When light is reflected
Show solution
Solution
Total internal reflection occurs when light travels from a denser medium to a rarer medium at an angle greater than the critical angle.
Correct Answer:
A
— When light travels from a denser to a rarer medium
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Q. In Young's double-slit experiment, what causes the formation of interference patterns?
A.
Reflection of light
B.
Refraction of light
C.
Superposition of waves
D.
Diffraction of waves
Show solution
Solution
The interference pattern is formed due to the superposition of waves from the two slits.
Correct Answer:
C
— Superposition of waves
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Q. In Young's double-slit experiment, what is the condition for constructive interference?
A.
d sin(θ) = (m + 0.5)λ
B.
d sin(θ) = mλ
C.
d sin(θ) = (m - 0.5)λ
D.
d sin(θ) = 0
Show solution
Solution
The condition for constructive interference in Young's double-slit experiment is d sin(θ) = mλ, where m is an integer.
Correct Answer:
B
— d sin(θ) = mλ
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Q. What effect does temperature have on the speed of sound in air?
A.
Increases with temperature
B.
Decreases with temperature
C.
No effect
D.
Depends on humidity
Show solution
Solution
The speed of sound in air increases with an increase in temperature.
Correct Answer:
A
— Increases with temperature
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Q. What happens to the frequency of light when it passes from one medium to another?
A.
It increases
B.
It decreases
C.
It remains the same
D.
It becomes zero
Show solution
Solution
The frequency of light remains constant when it passes from one medium to another; only the speed and wavelength change.
Correct Answer:
C
— It remains the same
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Q. What happens to the wavelength of a sound wave as its frequency increases, assuming the speed of sound remains constant?
A.
Wavelength increases
B.
Wavelength decreases
C.
Wavelength remains constant
D.
Wavelength becomes zero
Show solution
Solution
If the speed of sound is constant, an increase in frequency results in a decrease in wavelength.
Correct Answer:
B
— Wavelength decreases
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Q. What happens to the wavelength of light as it enters a medium with a higher refractive index?
A.
It increases
B.
It decreases
C.
It remains the same
D.
It doubles
Show solution
Solution
The wavelength decreases as light enters a medium with a higher refractive index.
Correct Answer:
B
— It decreases
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Q. What is the condition for constructive interference in two coherent waves?
A.
Path difference = (n + 0.5)λ
B.
Path difference = nλ
C.
Path difference = (n + 1)λ/2
D.
Path difference = (n - 0.5)λ
Show solution
Solution
Constructive interference occurs when the path difference between two coherent waves is an integer multiple of the wavelength, nλ.
Correct Answer:
B
— Path difference = nλ
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Q. What is the condition for constructive interference of two waves?
A.
Path difference is an odd multiple of half the wavelength
B.
Path difference is an even multiple of the wavelength
C.
Waves are out of phase
D.
Waves are in phase
Show solution
Solution
Constructive interference occurs when the path difference between two waves is an even multiple of the wavelength.
Correct Answer:
B
— Path difference is an even multiple of the wavelength
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Q. What is the critical angle for total internal reflection from glass (n=1.5) to air (n=1)?
A.
41.8 degrees
B.
48.6 degrees
C.
60 degrees
D.
90 degrees
Show solution
Solution
The critical angle can be calculated using sin(θc) = n2/n1, which gives θc = sin^(-1)(1/1.5) = 41.8 degrees.
Correct Answer:
A
— 41.8 degrees
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Q. What is the effect of a prism on white light?
A.
Reflection
B.
Refraction
C.
Dispersion
D.
Absorption
Show solution
Solution
A prism disperses white light into its constituent colors due to refraction.
Correct Answer:
C
— Dispersion
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Q. What is the effect of increasing the wavelength of light on the angle of refraction when entering a medium?
A.
It increases the angle
B.
It decreases the angle
C.
It has no effect
D.
It causes total internal reflection
Show solution
Solution
Increasing the wavelength generally increases the angle of refraction due to the change in refractive index.
Correct Answer:
A
— It increases the angle
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Q. What is the focal length of a converging lens if it forms a real image at a distance of 30 cm from the lens when the object is placed at 60 cm?
A.
10 cm
B.
20 cm
C.
30 cm
D.
40 cm
Show solution
Solution
Using the lens formula (1/f = 1/v - 1/u), we find f = 1/(1/30 - 1/60) = 20 cm.
Correct Answer:
B
— 20 cm
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Q. What is the focal length of a convex lens if it forms a real image at a distance of 30 cm from the lens when the object is placed at 15 cm?
A.
10 cm
B.
15 cm
C.
20 cm
D.
30 cm
Show solution
Solution
Using the lens formula 1/f = 1/v - 1/u, we find f = 1/(1/30 - 1/15) = 20 cm.
Correct Answer:
C
— 20 cm
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Q. What is the formula for the diffraction angle in a single-slit diffraction pattern?
A.
a sin(θ) = nλ
B.
a sin(θ) = (n + 0.5)λ
C.
a tan(θ) = nλ
D.
a cos(θ) = nλ
Show solution
Solution
The formula for the diffraction angle in a single-slit diffraction pattern is a sin(θ) = nλ.
Correct Answer:
A
— a sin(θ) = nλ
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Q. What is the formula for the observed frequency (f') in the Doppler effect when the source is moving towards a stationary observer?
A.
f' = f (v / (v - vs))
B.
f' = f (v + vs) / v
C.
f' = f (v - vs) / v
D.
f' = f (v / (v + vs))
Show solution
Solution
The formula for the observed frequency when the source is moving towards the observer is f' = f (v / (v - vs)).
Correct Answer:
A
— f' = f (v / (v - vs))
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Q. What is the frequency of a sound wave if its wavelength is 2 meters and the speed of sound is 340 m/s?
A.
170 Hz
B.
340 Hz
C.
680 Hz
D.
850 Hz
Show solution
Solution
Frequency (f) = Speed (v) / Wavelength (λ) = 340 m/s / 2 m = 170 Hz.
Correct Answer:
B
— 340 Hz
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Q. What is the law that describes the relationship between the angles of incidence and refraction?
A.
Snell's Law
B.
Newton's Law
C.
Hooke's Law
D.
Faraday's Law
Show solution
Solution
Snell's Law states that n1 * sin(θ1) = n2 * sin(θ2), where n is the refractive index and θ is the angle.
Correct Answer:
A
— Snell's Law
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Q. What is the primary function of a convex lens in optical instruments?
A.
To diverge light rays
B.
To converge light rays
C.
To reflect light rays
D.
To absorb light rays
Show solution
Solution
A convex lens converges light rays that are incident on it, focusing them to a point.
Correct Answer:
B
— To converge light rays
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