You shine light with a wavelength of 400 nm at two small slits (i and ii) and observe an interference pattern on a screen. what is the difference in path lengths between the light that travels from slit i to the first dark fringe of the pattern and the light that travels from slit ii to the same dark fringe?

2 x 10⁻⁷ m

Explanation:

Since the light from two slits interfere to form dark fringe on the screen ,

the path difference must be odd multiple of λ / 2 .

Since it is the first dark fringe the factor of odd multiple must be one.

So path difference must be

( 2n +1 ) x λ / 2 .

for first dark fringe

n = 0

path difference  =  λ / 2

400 x 10⁻⁹ / 2 m

= 2 x 10⁻⁷ m

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's a b and