NEET Physics Questions: Wave Optics

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A point object is placed in front of a thick plane
mirror as shown in figure. Find the location of
final image w.r.t. object.
 




"Bhautik" runs towards a plane mirror with a speed of $20 ms^{–1} $, what is the speed of his image ?




When an object moves towards a plane mirror with a certain speed, the image formed in the mirror also moves towards the object with the same speed. Hence, if 'Bhautik' runs towards the mirror at $20 ext{ ms}^{-1}$, his image will also move towards him at $20 ext{ ms}^{-1}$.
A ray of light is incident at an angle $ 30^\circ $ on a mirror, The angle between normal and reflected ray is ............




According to the law of reflection, the angle of incidence is equal to the angle of reflection. Therefore, if a ray of light is incident at an angle of $30^ ext{circ}$, the angle of reflection will also be $30^ ext{circ}$. The angle between the normal and the reflected ray will be twice the angle of reflection, which is $60^ ext{circ}$.
The no. of images formed between two parallel plane mirror are




$ no.of image = { 360 ^\circ \over \theta} = { 360 ^ \circ \over 0^\circ } = \infty $

To get five images of a single object one should have two plane mirrors at an angle of.........





To determine the angle between two plane mirrors to get a specific number of images, we can use the formula: \( n = \frac{360}{\theta} - 1 \), where \( n \) is the number of images formed and \( \theta \) is the angle between the mirrors. For five images, we set \( n = 5 \) and solve for \( \theta \): \( 5 = \frac{360}{\theta} - 1 \) \( 6 = \frac{360}{\theta} \) \( \theta = \frac{360}{6} = 60^\circ \). So the correct answer is 72 degrees.
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A Plane mirror produces a magnification of




A plane mirror always produces an image that is virtual, erect, and of the same size as the object. Therefore, the magnification produced by a plane mirror is +1. This means the size of the image is equal to the size of the object.

It is difficult to see through the fog because





Light is scattered by the droplets in the fog. This scattering of light causes multiple reflections and deflections, making it difficult for our eyes to see through the fog clearly. This phenomenon is known as Rayleigh scattering.

If a ray of light is incident on a plane mirror at an angle of $ 30 ^\circ $ then deviation produced by a plane mirror is_ ..........





$ here, 180 - 60 ^\circ = 120 ^\circ $

Which of the following colours is scattered minimum ?




wavelength maximum, Scattering is minimum

The head light of a jeep are 1.2 m apart. If the pupil of the eye of an observer has a diameter of 2 mm and light of wavelength $ 5836 A ^\circ $ is used what should be the maximum distance of the jeep from the observer if two head lights are just seem to be separated apart ?





$ use d \theta = { 1.22 \lambda \over D } = { x \over r } , where r = distant of jeep car $ $ \therefore r = 3.34 km $

Interference is possible in_




$ For, plano - convex lens , { 1 \over f_1 } = { 1 \over f_3 } = (n-1) \left( { 1 \over \infty } \times {1 \over R } \right) = {1 \over 24 }$ $ For , double convex lens \therefore { 1 \over f_1} + {1 \over f_2} +{ 1 \over f_3 }= { -1 \over 60 } $ $ \therefore {1 \over f_2} = { -1 \over 10 } $ $ now \therefore { 1 \over f_2 } = (n-1) \left( {1 \over R_1} - {1 \over R_2 }\right) = n =1.6 $
Huygin's wave theory of light can not explain_ phenomina.




Huygens' wave theory of light can explain wave phenomena such as diffraction and interference. However, it cannot explain the photoelectric effect, which requires the concept of light as particles (photons) as explained by Einstein's quantum theory.
The fringe width for red $ \beta _r ( \lambda_r = 8000 A ^ \circ) $ and the fringe width for violct $ \beta _\nu ( \lambda_\nu = 4000 A ^ \circ) $ then $ { \beta_r \over \beta_\nu } $




The fringe width (β) in a double-slit experiment is directly proportional to the wavelength (λ) of the light used. Given λ_r = 8000 Å and λ_ν = 4000 Å, the ratio of their fringe widths is β_r / β_ν = λ_r / λ_ν = 8000 Å / 4000 Å = 2:1.
In young's double slite experiment if the width of be cm 3rd fringe is $10 ^{-2} $ cm, then the width of 5th fringe will be ________cm




No explanation available.
The light waves from two coherent sources of same intensity interfere each other. Then what will be maximum intensity when minimum intensity is zero ?




When two coherent light waves of the same intensity (I) interfere constructively, the maximum intensity (I_max) is given by: \[ I_{ ext{max}} = 4I \] This is because the electric field amplitudes add up in constructive interference, resulting in the intensity being proportional to the square of the amplitude. Since the minimum intensity given is zero, the maximum intensity will be 4I.