Man wants to get a picture of a zebra. He photographed a white donkey after fitting a
glass, with black stripes on to the lens of his camera. What photo will he get? Explain.
Two converging lenses are to be placed in the path of parallel rays so that the rays remain
parallel after passing through both lenses. How should the lenses be arranged? Explain
with a neat ray diagram.
The focal length of a converging lens is 20cm. 2 cm. height object is 60cm from the lens.
Where will the image be formed and what kind of image is it? And also find the height of
the image
(Ans: A real, diminished, inverted image formed at 30cm from the lens)
A double convex lens has two surfaces of equal radii ‘R’ and refractive index n = 15. Find
the focal length ‘f’.
Harsha tells Siddhu that the double convex lens behaves like a convergent lens. But Siddhu
knows that Harsha’s assertion is wrong and corrected Harsha by asking some questions.
What are the questions asked by Siddhu?
Can a virtual image be photographed by a camera?
How do you appreciate the coincidence of the experimental facts with the results obtained
by a ray diagram in terms of behaviour of images formed by lenses?
Find the refractive index of the glass which is a symmetrical convergent lens if its focal
length is equal to the radius of curvature of its surface.
find the radii curvature of a convexo –concave convergent lens made of glass with
refractive index n=1.5 having focal length of 24cm. One of the radii of
curvature is double the other.
Higher Order Thinking Order
A convex lens is made up of three different materials as shown in the figure.
How many of images does it form?
You have a lens. Suggest an experiment to find out the focal length of the
lens.
