JAMB Physics Past Questions & Answers - Page 267

1,331.

The magnification of the image of an object placed in front of a convex mirror is \(\frac{1}{3}\). If the radius of curvature of the mirror is 24cm, what is the distance between its object and its image?

A.

8cm

B.

16cm

C.

24cm

D.

32cm

Correct answer is D

F = uv ; v = 1u

12 = \(\frac{v + 3v}{v + 3v}\)

v = 16cm, u = 48cm

distance between U and V

= 48 - 16 =32cm

1,332.

Light of wavelength 5000 x 10-8cm travels in free space with a velocity of 3 x 108ms-1. What is its wavelength in glass of refractive index 1.5?

A.

3333 x 10-8cm

B.

5000 x 10-8cm

C.

6666 x10-8cm

D.

750010-8cm

Correct answer is A

n = \(\frac{\text{wavelength in space}}{\text{wavelength in glass}}\)

1.5 = \(\frac{5000 \times 10^{-8}}{\lambda g}\)

\(\lambda\)g = 3333 x 10-8cm

1,333.

In a sound wave in air, the adjacent rarefactions and compressions are separated by a distance of 17cm. If the velocity of the sound wave is 340ms-1. Determine the frequency

A.

10Hz

B.

20Hz

C.

1000Hz

D.

5780Hz

Correct answer is C

\(\lambda\) = 2L

2 x 17 = 34cm

F = \(\frac{V}{\lambda}\)

= \(\frac{340}{34 \times 10^{-2}}\)

= 1000Hz

1,334.

When the tension in a sonometer wire is doubled, the ratio of the new frequency to the initial frequency is?

A.

\(\frac{1}{\sqrt2}\)

B.

\(\frac{1}{2}\)

C.

\(\sqrt2\)

D.

2

Correct answer is A

\(\frac{F_1}{F_2}\) = \(\sqrt{\frac{T_1}{T_2}}\)

\(T_2 = 2T_1\)

\(\frac{F_1}{F_2}\) = \(\sqrt{\frac{T_1}{2T_1}}\)

\(\frac{F_1}{F_2}\) = \(\sqrt2\)

F\(_2\) : F\(_1\) = 1 : \(\sqrt{2}\)

\(\frac{F_2}{F_1}\) = \(\frac{1}{\sqrt2}\)