Answer
given,
wavelength (λ) = 650 nm
angle = 5°
using bragg's law
d = 7.46 x 10⁻⁴ cm
number of slits per centimeter
= 
b) wavelength of two rays 650 nm and 420 nm
d = 2 x 10⁻6 m
we now,
for 650 nm
θ = 40.54°
for 450 nm
θ = 24.83°
now, difference
|θ_{650} -θ_{420}| =40.54°-24.83°
|θ_{650} -θ_{420}| =19.71°
The position of the centre of gravity of an object affects its stability. The lower the centre of gravity (G) is, the more stable the object. The higher it is the more likely the object is to topple over if it is pushed. Racing cars have really low centres of gravity so that they can corner rapidly without turning over.
Increasing the area of the base will also increase the stability of an object, the bigger the area the more stable the object. Rugby players will stand with their feet well apart if they are standing and expect to be tackled.
Media 1 and 2 are air and liquid. By Snell's law;
n1/n2 = Sin ∅2/Sin ∅1
Then,
n2 = (n1* Sin Ф1)/Sin ∅2 = (1*Sin 31.7)/Sin 21.3 = 1.4466.
When the light travels in the opposite direction and at critical angle, media 1 and 2 are liquid and air respectively while ∅2 = 90°
Therefore,
n1/n2 = Sin 90 / Sin ∅c => ∅c = Sin ^-1[n2*Sin 90]/n1 = Sin ^-1[1*Sin 90]/1.4466 = 43.73°
The critical angle (∅c) is 43.73°.
The horizontal speed has no effect on how long it takes to reach the ground.
A bullet shot from a gun and a bullet dropped from the front end of the gun
at the same time as the shot both hit the ground at the same time.
The number that counts is the height from which it fell . . . the 1.25 m.
I'll use this very useful formula:
Distance of free fall,
starting from rest = (1/2) · (gravity) · (time)²
1.25 m = (1/2) · (9.8 m/s²) · (time)²
Divide each side
by 4.9 m/s² : 1.25 m / 4.9 m/s² = time²
0.2551 sec² = time²
Square root each side: 0.505 sec = time
It looks like the correct choice is approximately 'A'. (rounded)
