Question

(a) (i) What is meant by the term ‘critical angle’? 

(ii) How is it related to the refractive index of the medium? 

(iii) Does the depth of a tank of water appear to change or remain the same when viewed normally from above? 

(b) A ray of light PQ is incident normally on the hypotenuse of a right angled prism ABC as shown in the diagram given alongside :

 

(i) Copy the diagram and complete the path of the ray PQ till it emerges from the prism. 

(ii) What is the value of the angle of deviation of the ray? 

(iii) Name an instrument where his action of the prism is used. 

(c) A converging lens is used to obtain an image of an object placed in front of it. The inverted image is formed between F₂ and 2F₂ of the lens. 

(i) Where is the object placed? 

(ii) Draw a ray diagram to illustrate the formation of the image. 

Answer 1

(a) (i) The angle of incidence in a denser medium for which angle of refraction in rarer medium is 90° is called critical angle. (ii) Refractive index (µ) = 1/sin C

(iii) The depth of tank remains same when viewed normally from above.