Athin film of oil of thickness t is floating on water. the oil has index of refraction no = 1.4. there is air above the oil. when viewed from the air in the direction normal to the surface, there is constructive interference of reflected red light with l = 675 nm. find the minimum thickness t of the oil film that will give constructive interference of reflected light with l = 675 nm.

t = 120.5 nm

Explanation:

given,    

refractive index of the oil = 1.4

wavelength of the red light = 675 nm

minimum thickness of film = ?

formula used for the constructive interference

where n is the refractive index of oil

t is thickness of film

for minimum thickness

m = 0

        t = 120.5 nm

hence, the thickness of the oil is t = 120.5 nm

answer: the exterior temperature of commercial jet planes as they leave the stratosphere and return to the ground increases steadily.

explanation:

the lower most layer of atmosphere is troposphere which extends from 0 to 12 km above the surface of the earth. the temperature initially decreases as distance is increased from the earth's surface. commercial jets fly in lower part of the stratosphere. the stratosphere extends upto 50 km. the temperature in stratosphere starts rising again due to presence of ozone which traps the uv rays.

thus, when the planes leave the stratosphere and return to the ground, the exterior temperature increases steadily.

it would be kevlar ^^