1. An Object approaches a converging lens with a uniform speed of 5 m/s and stops at the focus. How will the image move with respect to the lens? Specify its nature. [1 Marks]
OR
In a simple microscope, a convex lens of focal length 5 cm is used. Calculate the magnifying power when the object is placed at the focus of the lens. [1 Marks]
2. What is the power of an equiconvex lens of refractive index n2 dipped in a liquid of refractive index n1, where n1>n2? [1 Marks]
3. Assertion (A) : The angle of minimum deviation for a prism is lesser for red light than that for blue light.
Reason (R) : The refractive index of the material of a prism for blue light is greater than that for red light. [1 Marks]
4. A ray of light falls on a transparent sphere of n=√3 at an angle of incidence 60° with the diameter AB of the sphere having center C. The ray emerges from the sphere parallel to the line AB. Find the angle of emergence. [2 Marks]
5. i) Draw a ray diagram of an astronomical telescope in normal adjustment. Obtain an expression for its magnifying power. How can be increase the magnifying power of the telescope.
ii) A beam of light converges at a point P. A lens is placed in the path of the beam at a distance of 25 cm from P. The final image is formed at infinity. Calculate the power of the lens. [5 Marks]
OR
i) A coin is placed inside a denser medium. Why does it appear to be raised? Obtain an expression for the height through which the object appears in terms of refractive index of the medium and real depth.
ii) A compound microscope consists of an objective lens of focal length 2 cm and an eyepiece of focal length 6.25 cm separated by a distance of 15 cm. How far from the objective should an object be placed in order to obtain the final image at the least distance of distinct vision (25 cm)? Calculate the magnifying power of the microscope. [5 Marks]
[u₀=-2.5 cm m=-20]
2020
A composite prism ABC is made up of two identical right-angled prisms ABD and ADC made up of different materials of refractive indices √3 and µ respectively. A ray of light is incident on face AB of this prism at 60° as shown in the figure. It is observed that the
final emergent ray grazes along face AC. Find the value of µ.
PYQ
2017
(i) A ray of light incident of face AB of an equilateral glass prism, shows minimum deviation of 30°. Calculate the speed of light through the prism.
(ii) Find the angle of incidence at face AB, so that the emergent ray grazes along the face AC.
2020
An object is placed 30 cm in front of a plano-convex lens with its spherical surface of radius of curvature 20 cm. If the refractive index of the material of the lens is 1·5, find the position and nature of the image formed.
2019
An equilateral glass prism has a refractive index 1.6 in air. Calculate the angle of minimum deviation of the prism, when kept in a medium of refractive index 4√2/5.
Ans :
2019
δm=30°
2020
f=+40 cm, V=-120 cm, Nature : Virtual and Erect
2017
2.12×10^8 m/s, i=sin^-1(√2sin15°)
2020
µ=2
