HSSC-1 (Class-11) Solved Physics MCQs; Unit-9: Physical Optics; (New Book/KPK Text Board, Peshawar) With Verified Answers


1. The principle of Young's double slits experiment is based on the division of:




... Answer is D. Wavefront
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2. Which one of the following properties proves the transverse wave nature of light




... Answer is C. Polarization
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3. Coloured fringes observed in soap bubbles are the examples of




... Answer is B. Interference
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4. During a sunny day we see the objects in a classroom even when all the electric lights are off, due to




... Answer is C. Diffraction of light
The bending of a light wave around an obstacle and spreading into its geometrical shadow is called diffraction


5. The principle of the Michelson interferometer is based on the division of




... Answer is B. Amplitude
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6. In Young's double-slit experiment the separation between the slits is halved and the distance between the slits and the screen is doubled. The fringe width is




... Answer is D. Quadrupled
Formula for the width of fringes in Michelson interferometer experiment Δy = `\ frac {λL}{d}` 👉 when d' = `\ frac {d}{2}` and L' = 2 L 👉 Δy' = `\ frac {λ2L}{d/2}` = 4`\ frac {λL}{d}` = 4 Δy


7. Signal from a remote control to the device operated by its travels with the speed of: :




... Answer is B. Light
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8. Light of wavelength λ is incident normally on a diffraction grating for which the slit spacing is equal to 3λ. What is the sine of the angle between the second-order maximum and the normal? :




... Answer is C. `\ frac {2}{3}`
we have d sinθ = mλ 👉 when d = 3λ and m = 2 ( second order fringes) 👉 3λ sinθ = 2λ 👉 sinθ = `\ frac {2}{3}`


9. Which of the following gives three regions of the electromagnetic, spectrum in order of increasing wavelength, visible radiation




... Answer is C. Ultraviolet, infra-red microwaves
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10. Two monochromatic radiations X and Y are incident normally on a diffraction grating. The second-order intensity maximum for X coincides with the third-order intensity maximum for Y. What is the ratio ( wavelength of X)/(wavelength of Y)




... Answer is B. `\ frac {2}{3}`
Using Formula d sinθ = mλ 👉 For Radiation X d sinθ = m λx -----------eqn (1) 👉 For Radiation y d sinθ = m λy -----------eqn (1) diving eqn (2) by eqn (1) at m=2 for X radiation and m= 3 for Y radiation 👉 `\ frac {λx}{λy}` = `\frac {2}{3}`


11. The tip of a needle does not give a sharp image. It is due to




... Answer is C. Diffraction
The bending of a light wave around an obstacle and spreading into its geometrical shadow is called diffraction




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