A traveling electromagnetic wave in a vacuum has an electric field amplitude of 62.5 V/m. Calculate the intensity S of this wave. Then, determine the amount of energy that flows through area of 0.0231 m2 over an interval of 14.9 s, assuming that the area is perpendicular to the direction of wave propagation.

a) 5.19 W/m²

b) 1.79 J

Explanation:

For the calculation of intensity, I. We have

I = E(rms)² / (cμ), where

c = speed of light

μ = permeability of free space

I = (62.5 / √2)² / [(2.99 x 10^8) (1.26 x 10^-6)]

I = 1954 / 376.74

I = 5.19 W/m²

Therefore, the intensity, I = 5.19 W/m²

t = 14.9 s

A = 0.0231 m²

Amount if energy flowing, U = IAt

U = (5.19) (0.0231) (14.9) J

U = 1.79 J

answer: the correct answer is 1.

explanation: there are various process in which a radioactive nuclei decays:

1) alpha decay: in this process, a heavier nuclei decays into lighter nuclei by releasing alpha particle. the mass number is reduced by 4 units.

2) electron capture: in this decay process, a parent nuclei absorbs an electron and gets converted into a neutron. simply, a proton and an electron combines together to form a neutron. mass number does not change in this process.

3) gamma ray emission: it is a decay process in which an unstable nuclei gives excess energy by a spontaneous electromagnetic process. this decay releases . this process does not change the mass number.

4) positron emission: it is a type of decay process, in which a proton gets converted to neutron and an electron neutrino. this is also known as -decay. in this the mass number remains same.

from the above information, we see that only alpha-decay is producing a change in the mass number of the nucleus.

option number c is the right answer.