Answer:
<h2>Magnitude of the second charge is

</h2>
Explanation:
According to columbs law;
F = 
F is the attractive or repulsive force between the charges = 12N
q1 and q2 are the charges
let q1 = - 8.0 x 10^-6 C
q2=?
r is the distance between the charges = 0.050m
k is the coulumbs constant =9*10⁹ kg⋅m³⋅s⁻⁴⋅A⁻²
On substituting the given values
12 = 9*10⁹*( - 8.0 x 10^-6)q2/0.050²
Cross multiplying

Answer:
The last one is false
Explanation:
Energy can be neither created or destroyed. It can only move from one type of energy to another.
The answer would be A, as B refers to conduction and C and D refer to radiation. Convection is the transfer of different temperature currents, i.e, A
Answer:The rate of ejection of photoelectrons will increase
Explanation:
If the frequency of incident monochromatic light is held constant and its intensity is increased, the rate of ejection of photoelectrons from the metal surface increases with increase in intensity of the monochromatic light. More current flows due to more ejection of photoelectrons.
D = 1/f, where D is the power in diopters and f is the focal length in meters.
D=1/20
<u>D=0.05</u>