Question

1. A ray of light is incident on a plane mirror at an angle of 40°, relative to the normal of the mirror. If the normal of the mirror is rotated by an angle 10°, away from the incident ray, what is the new angle of reflection? A ray of light is incident on a plane mirror at an angle of 40°, relative to the normal of the mirror. If the normal of the mirror is rotated by an angle 10°, away from the incident ray, what is the new angle of reflection?

30°

10°

50°

4°

2. A RL circuit includes a 0.25 H inductor, which are connected to three identical resistors in parallel. If the circuit is to have a characteristic time of 0.225 s, what should be the resistance of the resistors used in the circuit?

2.22 Ω

3.33 Ω

0.222 Ω

0.370 Ω

Answer 1

1. 50° is the correct answer.

Explanations:-

Here initial angle of reflection was 40° so that when we change the normal angle by 10 ° away from the incident ray then the angle of reflection will also be change by the same angle with respect to the new angle of reference frame hence the new angle of reflection will be 50°

2 .3.33 is correct here.

Here we have given that,

L = 0.25

Time constant T = 0.225 s

Now the equivalent resistance of three resistance in parallel will be given as,

Req = R/3

So that the time constant for RL circuit will be,

T = L/Req = 3L/R

So that ,

R = 3L/T = 3 × 0.25 /0.225 = 3.33333333333 ohm

Which is our required answer of the value of resistance.