A bulb is located on a wall. Its image is to be obtained on a parallel wall with the help of convex lens. If the distance between parallel walls is 'd' then required focal length of lens placed in between the walls is : -
- only $\frac{d}{4}$
- only $\frac{d}{2}$
- more than $\frac{d}{4}$ but less than $\frac{d}{2}$
- less than $\frac{d}{4}$
The Correct Option is B
Solution and Explanation
We now know that in order for a convex lens to properly generate an image of an item on a screen, the distance (D) between the source and the screen must equal 4f, where f is the lens's focal length.
\(u = v = \frac{D}{2} = d\)
\(f = \frac{D}{4} = \frac{d}{2}\)
Top Questions on Refraction of Light
- A light ray is passing from air (refractive index \( \mu_1 = 1.0 \)) into water (refractive index \( \mu_2 = 1.33 \)). If the angle of incidence in air is 30°, what is the angle of refraction in water?
- MHT CET - 2025
- Physics
- Refraction of Light
Two light beams fall on a transparent material block at point 1 and 2 with angle \( \theta_1 \) and \( \theta_2 \), respectively, as shown in the figure. After refraction, the beams intersect at point 3 which is exactly on the interface at the other end of the block. Given: the distance between 1 and 2, \( d = 4/3 \) cm and \( \theta_1 = \theta_2 = \cos^{-1} \frac{n_2}{2n_1} \), where \( n_2 \) is the refractive index of the block and \( n_1 \) is the refractive index of the outside medium, then the thickness of the block is cm.
- JEE Main - 2025
- Physics
- Refraction of Light
- At the interface between two materials having refractive indices \( n_1 \) and \( n_2 \), the critical angle for reflection of an EM wave is \( \theta_c \). The \( n_1 \) material is replaced by another material having refractive index \( n_3 \), such that the critical angle at the interface between \( n_1 \) and \( n_3 \) materials is \( \theta_{c3} \). If \( n_1 > n_2 > n_3 \), \( \frac{n_2}{n_3} = \frac{2}{5} \), and \( \sin \theta_{c2} - \sin \theta_{c1} = \frac{1}{2} \), then \( \theta_{c1} \) is:
- JEE Main - 2025
- Physics
- Refraction of Light
- In a long glass tube, a mixture of two liquids A and B with refractive indices 1.3 and 1.4 respectively, forms a convex refractive meniscus towards A. If an object placed at 13 cm from the vertex of the meniscus in A forms an image with a magnification of \(-2\), then the radius of curvature of the meniscus is:
- JEE Main - 2025
- Physics
- Refraction of Light
- Mobility \( \mu \) of an electron is related to average collision time \( \tau \) as: \[ \mu = \frac{e \tau}{m} \] (where \( e \) is the electronic charge, and \( m \) is the mass of the electron)
- KEAM - 2024
- Physics
- Refraction of Light
Questions Asked in NEET exam
- What is the fate of a piece of DNA carrying only gene of interest which is transfered in to an alien organism?
A. The piece of DNA would be able to multiply itself independently in the progeny cells of the organism.
B. It may get integrated into the genome of the recipient.
C. It may multiple and be inherited along with the host DNA.
D. The alien piece of DNA is not an integral part of chromasame.
E. It shows ability to replicate.
Choose the correct answer from the options given below: - The magnetic moment of an iron bar is M. It is now bent in such a way that it forms an arc section of a circle subtending an angle of 60° at the centre. The magnetic moment of this arc section is
- NEET (UG) - 2024
- Magnetic moment
- Given below are certain cations. Using inorganic qualitative analysis, arrange them in increasing group number from 0 to VI.
A) Al3+
B) Cu2+
C) Ba2+
D) Co2+
E) Mg2+
Choose the correct answer from the options given below- NEET (UG) - 2024
- Modern Periodic Law And The Present Form Of The Periodic Table
- A compound X contains 32% of A, 20% of B and remaining percentage of C. Then, the empirical formula of X is:
(Given atomic masses of A=64; B=40; C=32 u)- NEET (UG) - 2024
- Some basic concepts of chemistry
Identify the major product C formed in the following reaction sequence:
- NEET (UG) - 2024
- Chemical Reactions
Concepts Used:
Refraction of Light
Refraction is the bending of a wave when it enters a medium where its speed is different. The refraction of light when it passes from a fast medium to a slow medium bends the light ray toward the normal boundary between the two media. The amount of bending depends on the indices of refraction of the two media and is described quantitatively by Snell's Law.
If you ever observe a pencil dipped into water, you’ll notice that it seems to be tilted at an angle at the interface of air and water, or the bottom of a tub or a tank that contains water seems to be raised. This phenomenon is caused due to the process of refraction of light. Refraction of light is the bending of the light wave, passing from one medium to another, which is caused due to the difference in the density of the two mediums.
Reason behind Refraction
The main cause of refraction is the variation in the velocity of the light when it enters different mediums. The speed of light in the air is faster than that of water. So, the speed of the light increases when it travels from water to air, and similarly, the speed decreases when it travels from air to water.
In the below figure, it is shown why the printed alphabets appear to have risen when seen through a glass slab. This is because when the light travels from air to glass, the speed gets reduced and the light moves toward the normal, that is the light rays move towards the NN’ normal from its original path. Likewise, when the light ray travels from glass to air, its speed gets increased and it moves away from the normal.
Refraction of Light in Reality
- Twinkling of the stars - The atmosphere is composed of areas of the thick and thin atmosphere. When one looks at the stars at night, the light passing through these different layers of the atmosphere from the stars reaches our eyes and therefore the stars appear to twinkle.
- As the light travels from the bottom to the top, the light coming from the pool bends due to refraction and thus the swimming pool always looks shallower than it really is.
- Due to the refraction of light, white light when passed through a prism splits into red, orange, yellow, green, blue and violet colours.
Laws of Refraction of Light
There are two Laws of Refraction. They are:
- The incident ray, the normal to the interface of two media, and the refracted ray, all lie on the same plane.
- Snell's Law: Snell’s law states that the ratio of the sine of the incident angle to the sin of refracted is constant. It describes the relationship between angles of refraction and angles of incidence.