Suppose we have a laser emitting a diffraction-limited beam (=632 nm) with a 2-mm diameter. How big a light spot from this laser would be produced on the surface of the Moon (distance to the Moon is R=376000 km)? Neglect any effects of the Earth’s atmosphere

Explanation:

λ = wave length = 632 x 10⁻⁹

slit width a = 2 x 10⁻³ m

angular separation of central maxima

= 2 x λ /a

= 2 x 632 x 10⁻⁹ / 2 x 10⁻³

= 632 x 10⁻⁶ rad

width in m of light spot.

= 632 x 10⁻⁶  x 376000 km

= 237.632 km

prolly a beacuse the momentuem the car has increases while going down hill

scattering of light by tiny particles in air to produce the colors we see on sky, is dependent on the following factors:

(i) wavelength of light

(ii) size of the scattering particle  

(iii) distance traveled by light through the atmosphere.

according to rayleigh's law of scattering, the amount of scattering is inversely proportional to the fourth power of its wavelength. shorter the wavelength, greater is its scattering. hence violet/blue light is scattered more than red.

sun's light is a composite light ( visible light) with wavelengths in the range 400 nm (violet) to 700 nm (red). as sunlight passes through our atmosphere, the molecules of air scatter light according to their wavelengths. during sunrise and sunset, the sun's position is below the horizon. hence light from the sun travels a greater distance in the atmosphere when compared to its position a noon.

as sunlight enters the earth's atmosphere, blue light is scattered away and at the end of its journey in the sky, only red and orange wavelengths remain in the beam.

hence at sunrise and sunset, the sky appears reddish orange.