Answer:
infra red radiation is used
Letter D: The amount of sleep a student gets affects student achievement
Theoretically, if the objects have the same mass and are moving towards each other at a speed of

, after a perfectly elastic collision, the object A is supposed to move with the same velocity in the opposite direction.
Answer:
(a) 
(b) 
(c)
(d)
Solution:
As per the question:
Refractive index of medium 1, 
Angle of refraction for medium 1, 
Angle of refraction for medium 2, 
Now,
(a) The expression for the refractive index of medium 2 is given by using Snell's law:

where
= Refractive Index of medium 2
Now,

(b) The refractive index of medium 2 can be calculated by using the expression in part (a) as:


(c) To calculate the velocity of light in medium 1:
We know that:
Thus for medium 1
(d) To calculate the velocity of light in medium 2:
For medium 2:
Given :
Number of operations move through a pocket calculator during a full day's operation ,
.
To Find :
How many coulombs of charge moved through it .
Solution :
We know , charge in one electron is :

So , charge on n electron is :

Therefore , -21.44 coulombs of charge is moved through it .
Hence , this is the required solution .