Interference
Q. In thin film interference, if the refractive index of the film is greater than that of the surrounding medium, what happens to the phase of the reflected wave?
A.
No phase change
B.
Phase change of π
C.
Phase change of 2π
D.
Phase change of λ
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Solution
When light reflects off a denser medium, it undergoes a phase change of π (180 degrees).
Correct Answer: B — Phase change of π
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Q. In thin film interference, what causes a phase change of π?
A.
Reflection from a denser medium
B.
Reflection from a rarer medium
C.
Transmission through a denser medium
D.
Transmission through a rarer medium
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Solution
A phase change of π occurs when a wave reflects off a denser medium.
Correct Answer: A — Reflection from a denser medium
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Q. In thin film interference, what happens to the colors observed when the thickness of the film increases?
A.
Colors become brighter
B.
Colors change
C.
Colors disappear
D.
Colors remain the same
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Solution
As the thickness of the film increases, the path difference changes, leading to a change in the observed colors due to interference.
Correct Answer: B — Colors change
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Q. In Young's double-slit experiment, if the distance between the slits is 0.2 mm and the distance from the slits to the screen is 1 m, what is the distance between the first and second bright fringes?
A.
0.1 mm
B.
0.2 mm
C.
0.4 mm
D.
0.6 mm
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Solution
Distance between fringes (y) = (λD)/d. Assuming λ = 500 nm, y = (500 x 10^-9 * 1)/(0.2 x 10^-3) = 0.0025 m = 0.25 mm. Distance between first and second bright fringes = 0.4 mm.
Correct Answer: C — 0.4 mm
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Q. In Young's double-slit experiment, if the distance between the slits is 0.2 mm and the distance to the screen is 1 m, what is the fringe width if the wavelength of light used is 500 nm?
A.
0.1 mm
B.
0.2 mm
C.
0.5 mm
D.
0.8 mm
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Solution
Fringe width (β) = λD/d. Here, D = 1 m, d = 0.2 mm = 0.0002 m, λ = 500 nm = 500 x 10^-9 m. β = (500 x 10^-9 * 1) / 0.0002 = 0.0025 m = 0.25 mm.
Correct Answer: A — 0.1 mm
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Q. In Young's double-slit experiment, if the distance between the slits is doubled while keeping the wavelength constant, what happens to the fringe width?
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
Fringe width (β) is given by β = λD/d, where D is the distance to the screen and d is the distance between the slits. If d is doubled, β halves.
Correct Answer: B — It halves
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Q. In Young's double-slit experiment, if the distance between the slits is doubled, what happens to the fringe width?
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
Fringe width is given by β = λD/d. If d (distance between slits) is doubled, the fringe width β will halve.
Correct Answer: B — It halves
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Q. Two coherent sources emit waves of the same frequency. If the path difference is 0.5λ, what type of interference occurs?
A.
Constructive interference
B.
Destructive interference
C.
No interference
D.
Partial interference
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Solution
Constructive interference occurs when the path difference is an integer multiple of λ.
Correct Answer: A — Constructive interference
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Q. Two coherent sources emit waves of the same frequency. If the phase difference between the waves is π radians, what type of interference occurs?
A.
Constructive interference
B.
Destructive interference
C.
No interference
D.
Partial interference
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Solution
A phase difference of π radians corresponds to a path difference of λ/2, leading to destructive interference.
Correct Answer: B — Destructive interference
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Q. Two coherent sources of light produce interference. If the path difference is 0.5λ, what type of interference occurs?
A.
Constructive interference
B.
Destructive interference
C.
No interference
D.
Partial interference
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Solution
Constructive interference occurs when the path difference is an integer multiple of λ, and 0.5λ corresponds to a half wavelength, leading to constructive interference.
Correct Answer: A — Constructive interference
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Q. Two coherent sources of sound produce waves of the same frequency. If the path difference between the waves at a point is 0.5 m, what is the phase difference at that point?
A.
0 rad
B.
π/2 rad
C.
π rad
D.
3π/2 rad
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Solution
Phase difference (Δφ) = (2π/λ) * path difference. For sound in air, λ = v/f. Assuming f = 1000 Hz and v = 340 m/s, λ = 0.34 m. Δφ = (2π/0.34) * 0.5 = π/2 rad.
Correct Answer: B — π/2 rad
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Q. Two coherent sources of sound produce waves of the same frequency. If the path difference between the waves is 0.5 m, what is the phase difference?
A.
0 rad
B.
π/2 rad
C.
π rad
D.
3π/2 rad
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Solution
Phase difference (φ) = (2π/λ) * path difference. Given λ = 1 m, φ = (2π/1) * 0.5 = π rad.
Correct Answer: B — π/2 rad
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Q. What happens to the interference pattern if one of the slits in a double-slit experiment is covered?
A.
Interference pattern disappears
B.
Pattern becomes brighter
C.
Pattern becomes dimmer
D.
Pattern becomes sharper
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Solution
Covering one slit eliminates the condition for interference, resulting in a single-slit diffraction pattern instead of an interference pattern.
Correct Answer: A — Interference pattern disappears
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Q. What happens to the interference pattern if the two slits in a double-slit experiment are no longer coherent?
A.
The pattern becomes sharper
B.
The pattern disappears
C.
The pattern becomes brighter
D.
The pattern remains unchanged
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Solution
If the two slits are not coherent, the interference pattern will disappear as the waves will not maintain a constant phase relationship.
Correct Answer: B — The pattern disappears
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Q. What happens to the interference pattern if the wavelength of light is increased?
A.
Fringe width decreases
B.
Fringe width increases
C.
Fringe pattern disappears
D.
Fringe width remains the same
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Solution
Increasing the wavelength increases the fringe width, as fringe width is directly proportional to the wavelength.
Correct Answer: B — Fringe width increases
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Q. What is the condition for constructive interference in a double-slit experiment?
A.
Path difference is an odd multiple of lambda/2
B.
Path difference is an even multiple of lambda
C.
Path difference is an odd multiple of lambda
D.
Path difference is zero
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Solution
Constructive interference occurs when the path difference between the two waves is an even multiple of the wavelength (nλ, where n is an integer).
Correct Answer: B — Path difference is an even multiple of lambda
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Q. What is the condition for constructive interference in a thin film?
A.
2t = (m + 1/2)λ
B.
2t = mλ
C.
t = mλ/2
D.
t = (m + 1/2)λ/2
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Solution
For constructive interference, the condition is 2t = mλ, where t is the thickness of the film and m is an integer.
Correct Answer: B — 2t = mλ
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Q. What is the condition for constructive interference in two waves?
A.
Path difference = (n + 1/2)λ
B.
Path difference = nλ
C.
Path difference = (n - 1/2)λ
D.
Path difference = 0
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Solution
Constructive interference occurs when the path difference is nλ, where n is an integer.
Correct Answer: B — Path difference = nλ
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Q. What is the effect of increasing the distance between the slits in a double-slit experiment on the fringe separation?
A.
Increases fringe separation
B.
Decreases fringe separation
C.
No effect
D.
Fringe separation becomes zero
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Solution
Increasing the distance between the slits decreases the fringe separation as fringe width is inversely proportional to the slit separation.
Correct Answer: B — Decreases fringe separation
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Q. What is the effect of increasing the distance between the slits in a double-slit experiment on the interference pattern?
A.
Fringe width increases
B.
Fringe width decreases
C.
Fringe intensity increases
D.
Fringe intensity decreases
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Solution
Increasing the distance between the slits decreases the fringe width, making the fringes closer together.
Correct Answer: B — Fringe width decreases
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Q. What is the effect of increasing the wavelength of light in a double-slit experiment?
A.
Fringe width decreases
B.
Fringe width increases
C.
Fringe separation remains unchanged
D.
No effect on interference pattern
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Solution
Increasing the wavelength (λ) increases the fringe width (β), as β is directly proportional to λ.
Correct Answer: B — Fringe width increases
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Q. What is the effect of increasing the wavelength of light used in a double-slit experiment on the fringe separation?
A.
Fringe separation decreases
B.
Fringe separation increases
C.
Fringe separation remains the same
D.
Fringe separation becomes zero
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Solution
Increasing the wavelength (λ) increases the fringe separation (β), as β is directly proportional to λ.
Correct Answer: B — Fringe separation increases
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Q. What is the formula for the fringe separation in a double-slit experiment?
A.
λD/d
B.
d/λD
C.
D/λd
D.
λd/D
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Solution
The fringe separation (β) is given by the formula β = λD/d, where λ is the wavelength, D is the distance to the screen, and d is the distance between the slits.
Correct Answer: A — λD/d
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Q. What is the formula for the fringe width in a double-slit experiment?
A.
λD/d
B.
d/λD
C.
D/λd
D.
λd/D
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Solution
The fringe width (β) is given by the formula β = λD/d, where D is the distance from the slits to the screen and d is the distance between the slits.
Correct Answer: A — λD/d
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Q. What is the maximum intensity ratio in interference of two waves of equal amplitude?
A.
1:1
B.
2:1
C.
4:1
D.
3:1
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Solution
Maximum intensity (I_max) = 4I_0 for two waves of equal amplitude (I_0). Thus, the ratio is 4:1.
Correct Answer: C — 4:1
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Q. What is the minimum thickness of a soap bubble that appears black in reflected light?
A.
λ/4
B.
λ/2
C.
λ
D.
3λ/4
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Solution
A soap bubble appears black in reflected light when the thickness is λ/4, leading to destructive interference.
Correct Answer: A — λ/4
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Q. What is the minimum thickness of a soap bubble that will appear black in reflected light?
A.
λ/4
B.
λ/2
C.
λ
D.
3λ/4
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Solution
A soap bubble appears black in reflected light when the thickness is λ/4, leading to destructive interference.
Correct Answer: A — λ/4
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Q. What is the minimum thickness of a soap film that appears dark when illuminated by white light?
A.
λ/4
B.
λ/2
C.
λ
D.
3λ/4
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Solution
For destructive interference in a soap film, the minimum thickness should be λ/2, considering the phase change upon reflection.
Correct Answer: B — λ/2
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Q. What is the phase difference between two waves that are in phase?
A.
0 radians
B.
π/2 radians
C.
π radians
D.
2π radians
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Solution
When two waves are in phase, their phase difference is 0 radians.
Correct Answer: A — 0 radians
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Q. What is the result of destructive interference when two waves of equal amplitude meet?
A.
Amplitude doubles
B.
Amplitude becomes zero
C.
Amplitude remains the same
D.
Phase difference is π
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Solution
Destructive interference occurs when two waves of equal amplitude meet out of phase, resulting in an amplitude of zero.
Correct Answer: B — Amplitude becomes zero
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