Optics

It occurs when light travels from denser to rarer medium, The angle of incidence must be greater than critical angle, It is used in optical fibers

Total internal reflection occurs when: (1) Light travels from optically denser to rarer medium, (2) Angle of incidence ≥ critical angle, (3) No refraction occurs - all light is reflected. It's the principle behind optical fiber communication.

Objective lens

In a compound microscope, the objective lens (closer to the object) produces the first real, inverted, and magnified image. This image then acts as an object for the eye lens, which produces the final virtual and magnified image.

1.49

At critical angle, sin(ic) = 1/n, where n is refractive index of denser medium. Given ic = 42°, so n = 1/sin(42°) = 1/0.669 = 1.49

Violet light has higher refractive index than red light, Dispersion occurs because refractive index depends on wavelength, White light separates into constituent colors

Dispersion occurs because refractive index increases with frequency (decreases with wavelength). Violet has highest frequency, so highest refractive index and maximum deviation. Red has lowest frequency, so lowest refractive index and minimum deviation.