WBJEE: Important Questions and Preparation Tips – Ray Optics

Oct 23, 2017 15:46 IST

WBJEE 2018: Ray Optics
WBJEE 2018: Ray Optics

In this article we bring to you chapter notes of chapter Ray Optics for WBJEE Entrance Examination 2018. About 2-3 questions are always asked from this chapter in WBJEE Entrance Examination.

These chapter notes include all important concepts and formulae of all topics of chapter Ray Optics like reflection, refraction, Snell’s law, Laws of refraction, mirror equation, magnification, Total Internal reflection, combination of lens, refraction through a prism etc. Some solved questions from previous year WBJEE Examination are also included in these chapter notes which will help you to understand the difficulty level of the coming WBJEE Examination 2018.

These notes can be used as a quick revision material to study important concepts instead of revising the complete chapter just before the examination.

About the exam:

West Bengal Joint Entrance Examination (WBJEE) is a state level common entrance test organized by West Bengal Joint Entrance Examinations Board for admission to the Undergraduate Level Engineering and Medical Courses through a common entrance test in the State of West Bengal.

Important Questions and Preparation Tips – Work, Power and Energy

Important Concepts:

WBJEE Important Concepts 1

WBJEE Important Concepts 2

WBJEE Important Concepts 3

Important Questions and Preparation Tips – Centre of Mass

Some previous years solved questions are given below:

Question 1:

A luminous object is separated from a screen by distance d. A convex lens is placed between the object and the screen such that it forms a distinct image on the screen. The maximum possible focal length of this convex lens is

(A) 4d

(B) 2d

(C) d/2

(D) d/4

Solution 1:

From the lens displacement method we can deduce that, the maximum possible focal length of the convex lens is d/4.

Hence, the correct option is (D).

Important Questions and Preparation Tips – Rotational Motion

Question 2:

An object is placed 30 cm away from a convex lens of focal length 10 cm and a sharp image is formed on a screen. Now a concave lens is placed in contact with the convex lens. The screen now has to be moved by 45 cm to get a sharp image again. The magnitude of focal length of the concave lens is (in cm)

(A) 72

(B) 60

(C) 36

(D) 20

Solution 2:

WBJEE Ray Optics solution 2

Hence, the correct option is (D).

Important Questions and Preparation Tips – Gravitation

Question 3:

A glass slab consists of thin u iform layers of progressively decreasing refractive indices RI (see figure) such that the RI of any layer is μ-mΔμ. Here μ and Δμ denote the RI of 0th layer and the difference in RI between any two consecutive layers, respectively. The integer m = 0, 1, 2, 3..... denotes the numbers of the successive layers. A ray of light from the 0th layer enters the 1st layer at an angle of incidence of 30°. After undergoing the mth refraction, the ray emerges parallel to the interface. If μ = 1.5 and Δμ = 0.015, the value of m is

WBJEE Ray Optics

(A) 20

(B) 30

(C) 40

(D) 50

Solution 3:

By using Snell’s law:

WBJEE Ray Optics Solution 3

Hence, the correct option is (D).

Important Questions and Preparation Tips – Simple Harmonic Motion

Question 4:

A ray of light strikes a glass plate at an angle of 60°. If the reflected and refracted rays are perpendicular to each other. the refractive index of glass is

WBJEE Ray Optics question 4

Solution 4:

WBJEE Ray Optics solution 4

Hence, the correct option is (D).

Important Questions and Preparation Tips – Laws of Motion

Question 5:

Light travels through a glass plate of thickness t and having refractive Index µ If c be the velocity of light in vacuum. time taken by the light to travel through this thickness of
glass is

WBJEE Ray Optics question 5

Solution 5:

WBJEE Ray Optics solution 5

Hence, the correct option is (C).

WBJEE 2017 Question Paper with Answer Key

Engineering Entrance Exam Calendar 2018: Important Dates

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