Q13 of 26 Page 1

(i) Which segment of electromagnetic waves has highest frequency? How are these waves produced? Give one use of these waves.

(ii) Which em waves lie near the high frequency end of visible part of em spectrum?


Give its one use. In what way this component of light has harmful effects on humans?


The segment of the electromagnetic waves having highest frequency is gamma rays. The gamma rays have no upper limit of frequency they occupy the position upper to the X rays.


The gamma rays have wide application in medicines and industries. The gamma rays are used for the treatment of cancer. In which it destroys the cancerous cells.


(ii) The segment of the electromagnetic spectrum that lies near the high frequency end of visible part is ultra violet rays.


Use: the ultraviolet rays are used to preserve the food material.


Harmful effects: The ultra violet radiations have harmful effect on human eyes and skin. It can cause skin cancer.


More from this chapter

All 26 →
11

(a) Define torque acting on a dipole of dipole moment p placed in a uniform electric field

Express it in the vector form and point out the direction along which it acts.


(b) What happens if the field is non-uniform?


(c) What would happen if the external field is increasing (i) parallel to and (ii) anti-parallel to ?


 12

(a) A point charge q moving with speed v enters a uniform magnetic field that is acting into the plane of the paper as shown. What is the path followed by the charge q and in which plane does it move?

(b) How does the path followed by the charge get affected if its velocity has a component parallel to?


(c) If an electric field is also applied such that the particle continues moving along the original straight-line path, what should be the magnitude and direction of the electric field ?



 14

In the following diagram, an object ‘O’ is placed 15 cm in front of a convex lens L1 of focal length 20 cm and the final image is formed at ‘I’ at a distance of 80 cm from the second lens L2. Find the focal length of the lens L2.


 15

Three rays (1, 2, 3) of different colours fall normally on one of the sides of an isosceles right-angled prism as shown. The refractive index of prism for these rays is 1.39, 1.47 and 1.52 respectively. Find which of these rays get internally reflected and which get only refracted from AC. Trace the paths of rays. Justify your answer with the help of necessary calculations.