Physics Questions & Answers - Free Online Practice

2,171.

Calculate the wavelength of a note which is one octave lower than a note of 256Hz in a medium in which the speed of sound is 352ms^-1

0.69m

1.38m

2.75m

5.50m

9.30m

View answer & explanation

Correct answer is B

\(\lambda\) = \(\frac{v}{f} = \frac{352}{256}\)

= 1.38

2,172.

A sonometer wire under a tension of N10N, produces a frequency of 250Hz when plucked. Keeping the length of the wire constant, the tension is adjusted to produce a new frequency of 350Hz. Calculate the new tension

39.2N

19.6N

14.2N

7.4N

5.1N

View answer & explanation

Correct answer is B

f \(\alpha\) \(\sqrt{T}\)

\(\frac{f_1}{f_2} = \sqrt{\frac{T_1}{T_2}}\)

\(\frac{250}{350} = \sqrt{\frac{10}{T_2}}\)

\(\frac{5}{7} = \sqrt{\frac{10}{T_2}}\)

\(\frac{25}{49} = \frac{10}{T_2}\)

T² = \(\frac{49 \times 10}{25} = 19.6\)

2,173.

The shortest length of the air column in a resonance tube at resonance is 0.12m and the next resonance length is 0.37m. Calculate the frequency of vibration given that the speed of sound in air is 340m^-1

1360Hz

694Hz

680Hz

34Hz

340Hz

View answer & explanation

Correct answer is C

f = \(\frac{v}{2(l_2 - l_1)} = \frac{340}{2(0.37 - 0.12)} = \frac{34}{0.5}\) = 680

2,174.

The intensity of light falling on the film in a camera depend on the

i. brightness of the object.
ii. diameter of the aperture stop.
iii. speed of the shutter.

Which of the statements is/are correct?

i, ii and iii

i and ii only

ii and iii only

iii only

View answer & explanation

Correct answer is E

No explanation has been provided for this answer.

2,175.

A lantern gives an image of 3m square of a slide 7.62cm square on a screen. If the screen is 10m from the projection lens of the lantern, calculate the focal length of the lens

40.3cm

26.1cm

24.8cm

0.7cm

0.3cm

View answer & explanation

Correct answer is C

M = \(\frac{V_H}{U_H} = \frac{300}{7.62}\)

= 39.3

U = \(\frac{V}{M} = \frac{1000}{39.3}\) = 25.44

\(\frac{1}{f} = \frac{I}{U} + \frac{I}{V} = \frac{I}{25.44} = \frac{I}{1000} = \frac{1025.44}{25440}\)

f = \(\frac{25440}{1025.44} = 24.8\)