Q. A beam of light passes through a narrow slit and produces a diffraction pattern. What happens to the width of the central maximum if the slit width is decreased? (2019)
A.
It increases
B.
It decreases
C.
It remains the same
D.
It becomes zero
Solution
According to the diffraction principle, as the slit width decreases, the width of the central maximum increases.
Q. A thin film of oil (n = 1.5) is on water (n = 1.33). What is the condition for destructive interference for light of wavelength 600 nm in air? (2022)
A.
2t = (m + 1/2)λ
B.
2t = mλ
C.
2t = (m + 1)λ
D.
2t = (m - 1/2)λ
Solution
For destructive interference in a thin film with a higher refractive index below, the condition is 2t = (m + 1/2)λ/n, where n is the refractive index of the film.
Q. If the wavelength of light used in a single-slit diffraction experiment is increased, what will happen to the position of the first minimum? (2022)
A.
It moves closer to the center
B.
It moves away from the center
C.
It remains unchanged
D.
It disappears
Solution
The position of the first minimum in single-slit diffraction is given by a sin(θ) = λ. Increasing λ will cause θ to increase, moving the minimum away from the center.
Q. In a double-slit experiment, if the distance between the slits is 0.1 mm and the screen is 1 m away, what is the fringe separation for light of wavelength 500 nm? (2020)
A.
0.5 mm
B.
0.1 mm
C.
0.2 mm
D.
0.3 mm
Solution
Fringe separation (β) = λD/d = (500 x 10^-9 m)(1 m)/(0.1 x 10^-3 m) = 0.5 mm.
Q. In a thin film of oil on water, which color will appear at the center of the pattern if the film thickness is such that it causes constructive interference for blue light? (2022)
A.
Red
B.
Green
C.
Blue
D.
Yellow
Solution
If the film thickness causes constructive interference for blue light, blue will appear at the center of the pattern.
Q. In a thin film of oil on water, which color will appear at the center of the pattern if the film is viewed in white light? (2022)
A.
Red
B.
Blue
C.
Green
D.
Yellow
Solution
At the center of the thin film interference pattern, the color that appears is typically green due to the constructive interference of wavelengths in that range.
Q. In a thin film of oil on water, which color will appear at the center of the pattern if the film thickness is such that it causes constructive interference for red light? (2022)
A.
Red
B.
Blue
C.
Green
D.
Yellow
Solution
The color that appears at the center of the pattern corresponds to the wavelength that experiences constructive interference, which in this case is red light.
Q. What is the maximum number of bright fringes observed in a double-slit experiment if the wavelength of light is 500 nm and the distance between the slits is 0.1 mm? (2020)
A.
5
B.
10
C.
20
D.
15
Solution
The maximum number of bright fringes is given by the formula n = d/λ. Here, n = 0.1 mm / 500 nm = 200, which means 20 bright fringes can be observed on either side of the central maximum.
Q. What is the maximum number of bright fringes that can be observed in a double-slit experiment with a given wavelength? (2023)
A.
Depends on the slit width
B.
Depends on the distance to the screen
C.
Depends on the wavelength and slit separation
D.
Always infinite
Solution
The maximum number of bright fringes depends on the wavelength and the slit separation, as it determines how many integer multiples of the wavelength fit within the observable range.
Correct Answer:
C
— Depends on the wavelength and slit separation