PHYSICS Geometrical Optics Presented by Kusagatti T A PHYSICS Q 1 : Let the x-y plane be the .(AIEEE 2011) boundary between two transparent media. Medium 1 in z ≥ 0 has a refractive index of √2 and medium 2 with z < 0 has a refractive index of √3. A ray of light in medium 1 given by the vector A = 6√3i +8√3j -10k is incident on the plane of separation. The angle of refraction in medium 2 is? a)45o b)60o c)75o d)30o PHYSICS Sol.1: ray is A = 6√3i +8√3j -10k H ere x-y plane is boundary between two media. cos i = |[OZ/√Ax2+Ay2+Az2]| = [10/ √36x3+64x3+100 =10/ √400 = ½ → i =600 From Snell’s law sin i / sin r = √3/√ 2 r = 45O Ans (a) PHYSICS Q 2. A ray of light traveling in water is incident on its surface open to air. The angle of incidence is θ, which is less than the critical angle. Then there will be a)Only reflected ray and no refracted ray b)Only a refracted ray and no reflected ray c) A reflected ray and a refracted ray and the angle between them would be less than 180- 2θ d)A reflected ray and a refracted ray and the angle between them would be greater than 180-2θ PHYSICS Sol.2: L ight is traveling from denser to rarer medium i.e. r > θ X+r+ θ =180 X = 180 – r – θ X < 180 - 2 θ |since r > θ Ans (C) PHYSICS Q.3 : A ball is dropped from (IIT – JEE 2009) a height of 20 m above the surface of water in a lake. The refractive index of water is 4/3. A fish inside the lake, in the line of fall of the ball, is looking at the ball. At an instant, when the ball is 12.8 m above the water surface, the fish sees the speed of ball as (a) 9 ms-1 (b) 12 ms-1 (c) 16 ms-1 (d) 21.33 ms-1 PHYSICS Sol.3 For freely falling body v2 =u2 +2gh Ans = (c) PHYSICS Q.4. A light ray traveling in a (IIT-2011) glass medium is incident on a glass –air interface at an angle of in cidence θ. The reflected (R) and transmitted (T) intensities, both as function of θ, are plotted. The correct sketch is PHYSICS Sol.4 If the angle of incidence is greater than critical angle, no light is transmitted. Hence intensity of transmitted light become zero. If Ө<C, maximum light is transmitted. And very little light is reflected Ans = ( c ) PHYSICS Q.5. A ray OP of monochromatic (IIT-2010) light is incident on the face AB of prism ABCD near vertex B at an incident angle of 600. If the refractive index of the material of the prism is√3, which of the following is (are) correct? (a)The ray gets totally internally reflected at face CD (b) The ray comes out through face AD (c) The angle between the incident ray and the emergent ray is 1200 (d)all the above