JAMB Physics Past Questions & Answers - Page 259

1,291.

Which of the following phenomena explains the formation of a mirage?

i. Reflection
ii. Refraction
iii. Diffraction

A.

i and ii only

B.

ii and iii only

C.

i and iii only

D.

i, ii, and iii only

Correct answer is A

No explanation has been provided for this answer.

1,292.

An object is placed 10cm in front of a concave mirror of focal length 15cm. What is the position and nature of the image formed?

A.

30cm and virtual

B.

6cm and real

C.

6cm and virtual

D.

30cm and real

Correct answer is A

F = \(\frac{uv}{u + v}\)

15 = \(\frac{10 \times v}{10 + v}\)

v = -30cm

1,293.

To obtain a magnification of 2.5, how far should an object be placed from the pole of a thin converging lens of focal length 10.20m?

A.

0.13m

B.

0.25m

C.

0.28m

D.

0.50m

Correct answer is C

v = 2.5u

F = \(\frac {uv}{u + v}\)

0.2 = \(\frac {u \times 2.5u}{u + 2.5u}\)

u = 0.28m

1,294.

Two strings of the same length and under the same tension gives notes of frequencies in the ratio 4 : 1. The masses of the strings are in the corresponding ratio of

A.

2 : 1

B.

1 : 2

C.

1 : 4

D.

1 : 16

Correct answer is D

F = \(\frac{1}{2L}\)\(\sqrt\frac{T}{m}\)

\(\frac{F_1}{F_2}\) = \(\sqrt\frac{m_2}{m_1}\)

\(\frac{1}{4}\) = \(\sqrt\frac{m_2}{m_1}\)

\(\frac{m_2}{m_1}\) = \(\frac{1}{16}\)

1,295.

A slight loading of a tuning fork has the effect of

A.

decreasing its amplitude

B.

increasing its amplitude

C.

decreasing its frequency

D.

increasing its frequency

Correct answer is C

When the prongs of the tuning fork are loaded, it causes an increase in their inertia, thereby decreasing the frequency of the fork.