back to directory
NEET PHYSICSWave OpticsEasy

Question

In Young's double-slit experiment, a student observes 8 fringes in a certain segment of the screen when a monochromatic light of 600 nm wavelength is used. If the wavelength of light is changed to 400 nm, then the number of fringes he would observe in the same region of the screen is:

A

12

B

6

C

8

D

9

Step-by-Step Solution

  1. Identify Given Values:
  • Initial number of fringes (n1n_1) = 8
  • Initial wavelength (λ1\lambda_1) = 600 nm600 \text{ nm}
  • Final wavelength (λ2\lambda_2) = 400 nm400 \text{ nm}
  • The segment of the screen (width LL) remains constant.
  1. Formula: The width of the region occupied by nn fringes is given by L=nβL = n \beta, where β=λDd\beta = \frac{\lambda D}{d} is the fringe width. Thus, L=nλDdL = \frac{n \lambda D}{d}.
  2. Relation: Since L,D,L, D, and dd are constant, the product of the number of fringes and the wavelength is constant: n1λ1=n2λ2n_1 \lambda_1 = n_2 \lambda_2
  3. Calculation: 8×600 nm=n2×400 nm8 \times 600 \text{ nm} = n_2 \times 400 \text{ nm} 4800=n2×4004800 = n_2 \times 400 n2=4800400=12n_2 = \frac{4800}{400} = 12
  4. Conclusion: The number of fringes observed with the new wavelength is 12.

Exam Context & Concepts Covered

This question aligns with the NEET PHYSICS syllabus, specifically targeting concepts from Wave Optics. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

PHYSICSWave Opticsyoungsdoubleslitexperimentstudentobserves

More Wave Optics Questions

View all

The interference pattern is obtained with two coherent light sources of intensity ratio $n$. In the interference pattern, the ratio $\frac{I_{max}-I_{min}}{I_{max}+I_{min}}$ will be

A.$\frac{\sqrt{n}}{n+1}$
B.$\frac{2\sqrt{n}}{n+1}$
C.$\frac{\sqrt{n}}{(n+1)^2}$
D.$\frac{2\sqrt{n}}{(n+1)^2}$
MediumSolve

At the first minimum adjacent to the central maximum of a single slit diffraction pattern, the phase difference between the Huygen's wavelet from the edge of the slit and the wavelet from the midpoint of the slit is

A.$\pi/4$ radian
B.$\pi/2$ radian
C.$\pi$ radian
D.$\pi/8$ radian
MediumSolve

A major breakthrough in the studies of cells came with the development of an electron microscope. This is because:

A.the resolution power of the electron microscope is much higher than that of the light microscope.
B.the resolving power of the electron microscope is 200-350 nm compared to 0.1-0.2 nm for the light microscope.
C.electron beam can pass through thick materials, whereas light microscopy requires thin sections.
D.the electron microscope is more powerful than the light microscope as it uses a beam of electrons that has a wavelength much longer than that of photons.
MediumSolve

Two slits in Young's experiment have widths in the ratio of $1:25$. The ratio of intensity at the maxima and minima in the interference pattern $\frac{I_{max}}{I_{min}}$ is:

A.$\frac{9}{4}$
B.$\frac{121}{49}$
C.$\frac{49}{121}$
D.$\frac{4}{9}$
MediumSolve

For a parallel beam of monochromatic light of wavelength $\lambda$, diffraction is produced by a single slit whose width $a$ is much greater than the wavelength of the light. If $D$ is the distance of the screen from the slit, the width of the central maxima will be:

A.$\frac{2D\lambda}{a}$
B.$\frac{D\lambda}{a}$
C.$\frac{Da}{\lambda}$
D.$\frac{2Da}{\lambda}$
EasySolve

In a diffraction pattern due to a single slit of width $a$, the first minimum is observed at an angle $30^\circ$ when light of wavelength $5000\text{ \AA}$ is incident on the slit. The first secondary maximum is observed at an angle of

A.$\sin^{-1}\left(\frac{2}{3}\right)$
B.$\sin^{-1}\left(\frac{1}{2}\right)$
C.$\sin^{-1}\left(\frac{3}{4}\right)$
D.$\sin^{-1}\left(\frac{1}{4}\right)$
MediumSolve

In a double-slit experiment, when light of wavelength $400 \text{ nm}$ was used, the angular width of the first minima formed on a screen placed $1 \text{ m}$ away, was found to be $0.2^{\circ}$. What will be the angular width of the first minima, if the entire experimental apparatus is immersed in water? $\left(\mu_{\text{water}} = \frac{4}{3}\right)$

A.$0.1^{\circ}$
B.$0.266^{\circ}$
C.$0.15^{\circ}$
D.$0.05^{\circ}$
MediumSolve

For Young's double-slit experiment, two statements are given below: Statement I: If screen is moved away from the plane of slits, angular separation of the fringes remains constant. Statement II: If the monochromatic source is replaced by another monochromatic source of larger wavelength, the angular separation of fringes decreases.

A.Statement I is False but Statement II is True.
B.Both Statement I and Statement II are True.
C.Both Statement I and Statement II are False.
D.Statement I is True but Statement II is False.
MediumSolve

Why 32,000+ students choose TopperSquare

Everything you need to crack NEET

15,000+ Chapter MCQs

Physics, Chemistry, Biology — chapter-wise, topic-wise practice

AI Performance Analytics

Know your weak topics. Get a personalised study plan.

Full NEET Mock Tests

180 questions, timed, with detailed score analysis

PYQ Sets 2010–2024

15 years of past papers with solved explanations

Start Practising Free

No credit card · 30-second signup · Free forever plan included

This neet physics practice question is part of the TopperSquare free question bank. TopperSquare offers 15,000+ chapter-wise NEET MCQs across Physics, Chemistry, and Biology with detailed step-by-step explanations, full mock tests, NEET PYQs (2010–2024), and an AI-powered performance analytics dashboard. browse all neet practice questions → · practice physics sets →

Explore more subjects:Physics MCQs•Chemistry MCQs•Biology MCQs•Botany MCQs•Zoology MCQs•NEET Mock Tests•NEET PYQs