Answer:

Explanation:
It is given that,
Initially, the electron is in n = 7 energy level. When it relaxes to a lower energy level, emitting light of 397 nm. We need to find the value of n for the level to which the electron relaxed. It can be calculate using the formula as :


R = Rydberg constant, 

Solving above equation we get the value of final n is,

or

So, it will relax in the n = 2. Hence, this is the required solution.
Answer:
d. lower than the original pitch and decreasing as he falls.
Explanation:
As per the Doppler effect when the pitch of the sound increases as the source approaches the observer and decreases as the source moves away. A classic example of this increasing pitch of ambulance siren as it approaches you and decreasing pitch of the siren as it goes away from you.
The same effect is applicable here as well. As the character keep falling, it is moving away from the observer so the pitch of his scream will keep on decreasing.
Background research is used to familiarize yourself with the topic or problem you're conducting your experiment on and help you form an educated guess explaining or solving it that will become your hypothesis.
Answer: (a) Smaller charge is
and larger charge is
.
(b) Smaller charge is
and larger charge is
.
Explanation:
(a) When both the spheres have same charge then force is repulsive in nature as like charges tend to repel each other.
Therefore, total charge on the two non-conducting spheres will be calculated as follows.

= 
Therefore, force between the two spheres will be calculated as follows.
F = 
12 N = 

or, 



This means that smaller charge is
and larger charge is
.
(b) When force is attractive in nature then it means both the charges are of opposite sign.
Hence, total charge on the non-conducting sphere is as follows.


Now, force between the two spheres is calculated as follows.
F = 
12 N = 



Hence, smaller charge is
and larger charge is
.