Q. In a Newton's ring experiment, if the radius of the first dark ring is found to be r, what is the radius of the second dark ring? (2020)
A.r
B.2r
C.√2r
D.r/2
Solution
The radius of the dark rings in Newton's rings is proportional to the square root of the ring number. Thus, the second dark ring will have a radius of 2r.
Q. In a thin film of oil on water, which color of light is most likely to be reflected? (2022)
A.Red
B.Blue
C.Green
D.Yellow
Solution
Due to the phenomenon of thin film interference, the color that is most prominently reflected depends on the thickness of the film and the wavelength of light. Typically, blue light is more likely to be reflected due to shorter wavelengths.
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 destructive interference for red light? (2022)
A.Blue
B.Green
C.Yellow
D.Red
Solution
Destructive interference for red light means red light is canceled out, leaving the shorter wavelengths (blue) visible.
Q. What is the angle of diffraction for the first minimum in a single-slit diffraction pattern if the slit width is 0.5 mm and the wavelength of light is 500 nm? (2023)
A.30°
B.60°
C.45°
D.15°
Solution
The angle for the first minimum is given by sin θ = λ/a, where a is the slit width. Thus, sin θ = 500 nm / 0.5 mm = 0.001, leading to θ ≈ 30°.
Q. What is the wavelength of light if the first-order maximum occurs at an angle of 30° in a double-slit experiment with a slit separation of 0.1 mm and a screen distance of 1 m? (2019)
A.0.5 mm
B.0.3 mm
C.0.2 mm
D.0.1 mm
Solution
Using the formula λ = d sin θ / m, where d = 0.1 mm, θ = 30°, and m = 1, we find λ = 0.1 mm * sin(30°) = 0.1 mm * 0.5 = 0.05 mm = 0.2 mm.
