Physics questions and answers

Physics Questions and Answers

If you want to learn more about the nature and properties of matter and energy or you're simply preparing for a Physics exam, these Physics past questions and answers are ideal for you.

506.

A ray of light passes through the centre of curvature of a concave mirror and strikes the mirror. At what angle is the ray reflected?

A.

180\(^o\)

B.

90\(^o\)

C.

0\(^o\)

D.

60\(^o\)

Correct answer is C

- a ray of light passing through the centre of a curvature is returned along the same path

- angle difference along the same path is zero

507.

The distance between an object and its real image in a convex lens is 40cm. If the magnification of the image is 3, calculate the focal length of the lens

A.

6.5 cm

B.

7.5 cm

C.

8.5 cm

D.

4.5 cm

Correct answer is B

u + v = 40

\(\frac{v}{u}\) = 3

v = 3u

u + 3u = 40

4u = 40

u = 10cm

v = 3u = 30cm

f = \(\frac{uv}{u + v} = \frac{10(30)}{10 + 30} = \frac{300}{40}\)

= 7.5 cm

508.

When the temperature of a liquid is increased, its surface tension?

A.

increases

B.

decreases

C.

remain constant

D.

increases then decreases

Correct answer is B

Surface tension or elasticity of a fluid decreases with increased  temperature

509.

Ripple in a power supply unit is caused by

A.

using an alternating current source

B.

forward voltage drop

C.

heavy load

D.

using a zener diode

Correct answer is A

The fluctuation of d.c signal results from the rectification of A.C source to d.c.

510.

Which of the following equations is the correct definition of the reactance of an indicator L?

A.

Reactance = (Amplitude of voltage) \(\div\) (Amplitude of current)

B.

Reactance = (Amplitude of voltage) x (Amplitude of current)

C.

Reactance = (Amplitude of current)\(^2\) \(\div\) (Amplitude of voltage)

D.

Reactance = (Amplitude of current)\(^2\) \(\div\) (Amplitude of voltage)\(\frac{1}{2}\)

Correct answer is A

Reactance is the value of an indicator or a capacitor in ohms