56) The device used to measure the specific heat of a substance is
A) micrometer
B) spectrometer
C) calorimeter
D) barometer
57) If I and are the angles of incidence and refraction respectively, then i
A) denser to rarer medium
B) rarer to denser medium
C) throughout denser medium only
D) throughout rarer medium only
58) The physical quantity which has no units, is
A) radius of curvature
B) velocity of light
C) focal length
D) refractive index
59) A rectangular tank of depth 2m is full of water of refractive index 
. When viewed from the top, the bottom of the tank is seen at a depth of
A) 2.66m
B) 1.5m
C) 1.33m
D) 3.33m
Explanation:Apparent depth = Real depth / Refractive index
60) When we sit at a camp fire, objects beyond the fire are seen swaying. The principle involved in it is
A) refraction
B) reflection
C) total internal reflection
D) dispersion