How To Prepare The Unit Light For NSEJS

Updated on Nov 01, 2022 09:08 AM IST

The NSEJS Physics section has questions from CBSE Class 9 and 10 chapters. Knowledge of Science chapters of lower classes and mathematics till Class 10 is preferred. Light is one of the important units from the NSEJS syllabus. The unit Light in the NCERT book has two chapters namely Light Reflection And Refraction and The Human Eye And The Colourful World. Careers360 helps you understand the top tips to prepare Light for NSEJS.

How To Prepare The Unit Light For NSEJS

Light Topics From NSEJS Syllabus

Reflection by curved surface, spherical mirror, mirror formula and magnification, refraction and laws refraction, refractive index, spherical lens and refraction through spherical lens, lens formula, magnification and power of lens, refraction through a prism, scattering and dispersion of light, Functioning of a lens in the human eye, defects of vision and their corrections, applications of spherical mirrors, lenses, diffraction and scattering and applications in daily life.

Also Read| How To Prepare Force And Laws Of Motion For NSEJS

Tips To Prepare NSEJS For Light

Understand all the basic terms like radius of curvature, focal length, principle axis, centre of curvature etc.
Understand the sign convention.
Study the ray diagram and image properties at different positions of objects.
Study all the formulas and practice problems using the formulas.
Solve all the NCERT and NCERT exemplar problems from the unit Light.
Practice NSEJS previous year papers.

Also Read| How To Prepare The Chapter On Motion For NSEJS

Important Formulas For Light

Formula

Description

Mirror equation:

1/v+1/u=1/f

u is object distance, v is the image distance F is the focal length of the mirror.

Magnification of a mirror

$m= \frac{h_{i}}{h_{o}}= \frac{-v}{u}$

$h_{i}=$ height of the image from the principal axis

$h_{o}=$ height of the object from the principal axis

$\boldsymbol{\frac{n_2}{n_1} = \frac{\sin \left ( \frac{D _{m}+A}{2} \right )}{\sin \left ( A/2 \right )}}$

A is the angle of the prism

Dm is the angle of minimum deviation

Thin lens formula

$\frac{1}{v}-\frac{1}{u}= \frac{1}{f}$

Lens makers formula

$\boldsymbol{\frac{1}{f}= \left ( \frac{\mu _{2}}{\mu _{1}}-1 \right )\left ( \frac{1}{R_{1}}- \frac{1}{R_{2}}\right )}$

$\mu _{1}=$ the refractive index of the medium of the object

$\mu _{2}=$ the refractive index of the lens

$R_{1}\, and \, R_{2}$ are the radius of curvature of two surface

Power of a lens

$\boldsymbol{P=\frac{1}{f}}$

Where P is the power and f is the focal length in metres

NSEJS Previous Year Questions For practice

Q-1- A glass plate of uniform thickness t and refractive index µ is as shown in the diagram. AB is the incident ray and FG is the emergent ray. The angles of incidence and refraction are i and r respectively. The perpendicular distance FC = x between the incident and the emergent rays is called the lateral shift. Then (NSEJS 2021-More Than one option is true)

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Q-2- Two illuminated point objects O1 and O2 are placed at a distance 24 cm from each other along the principal axis of a thin convex lens of focal length 9 cm such that images of both the objects are formed at the same position. Then the respective distances of the lens from O1 and O2 (in cm) are (NSEJS 2020)

(a) 12 and 12 (b) 18 and 6 (c) 14 and 10 (d) 16 and 8

Q-3- In a screw-nut assembly (shown below) the nut is held fixed in its position and the screw is allowed to rotate inside it. A convex lens (L) of focal length 6.0 cm is fixed on the nut. An object pin (P) is attached to the screw head. The image of the object is observed on a screen Y. When the screw head is rotated through one rotation, the linear distance moved by the screw tip is 1.0 mm. The observations are made only when the image is obtained in the same orientation on the screen. At a certain position of P, the image formed is three times magnified as that of the pin height. Through how many turns should the screw head be rotated so that the image is two times magnified?(NSEJS 2019)

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(a) 8 (b) 10 (c) 12 (d) 14

Q-4- The triangular face of a crown glass prism ABC is isosceles. Length AB = length AC and the rectangular face with edge AC is silvered. A ray of light is incident normally on a rectangular face with edge AB. It undergoes reflections at AC and AB internally and it emerges normally through the rectangular base with edge BC. Then angle BAC of the prism is____(NSEJS 2019)

a) 24º (b) 30º (c) 36º (d) 42º

Q-5- : The radius of curvature of a convex mirror is 'x'. The distance of an object from focus of this mirror y

(a) y ² / 4x (b) x ² / y (c) x ² / 4y (d) 4y²/ x