Optics Answers

A telescope is made of an object glass of focal length 20cm and an eyepiece of 5cm, both converging lenses. Find the magnification when the eye is focused to receive parallel rays.

Explain the essential features of a refracting telescope. Define and deduce an expression for the magnifying power of this instrument.

The image obtained with a converging lens is erect and three times the length of the object. The focal length of the lens is 20cm. Calculate the object and image distances.

The image of a real object in a diverging lens of focal length 10cm is formed 4cm from the lens. Find the object distance and the magnification. Draw a sketch to illustrate the formation of the image.

What do you know about the image obtained with a diverging(concave) lens? Explain briefly.

An object is placed

(i) 12cm

(ii) 4cm from a converging (convex) lens of focal length 6cm. Calculate the image position and the magnification in each case and draw sketches illustrating the formation of the image.

The refractive index of the glass of a prism for red light is 1.514 and for blue light is 1.523. Calculate the difference in the velocities of the red and blue light in the prism if the velocity of light in vacuum is 3 x 10^(5) km/second.

Describe fully

(a) One natural phenomenon due to total internal reflection.

(b) one practical application of it.

Explain the meaning of critical angle and total internal reflection

State the laws of refraction and define refractive index.