A source of sound produces waves in air of wavelengths 1.70m. If the speed of sound in air is 340m s-1, what is the period of vibration in second is? (a) 0.05s (b) 0.02s (c) 0.001s (d) 0.7s

Here are the solutions to the remaining objective questions:

Question 22: A body stands infront of a tall wall and produces a sound. If he hear the echo 3s later. Calculate his distance from the wall (V = 330ms⁻¹)

• Given: Total time for echo $t = 3 \text{ s}$, Velocity $V = 330 \text{ m/s}$.
• The time for the sound to travel one way to the wall is half of the total time: $$t_{one-way} = \frac{t}{2} = \frac{3 \text{ s}}{2} = 1.5 \text{ s}$$
• Calculate the distance $d$ using the formula $d = V \times t_{one-way}$: $$d = 330 \text{ m/s} \times 1.5 \text{ s} = 495 \text{ m}$$
• The correct answer is (a) 495m.

Question 23: How far from a hill should a boy stand in order to hear the echo of his clap 1.6s later (V = 340ms⁻¹)

• Given: Total time for echo $t = 1.6 \text{ s}$, Velocity $V = 340 \text{ m/s}$.
• The time for the sound to travel one way to the hill is half of the total time: $$t_{one-way} = \frac{t}{2} = \frac{1.6 \text{ s}}{2} = 0.8 \text{ s}$$
• Calculate the distance $d$ using the formula $d = V \times t_{one-way}$: $$d = 340 \text{ m/s} \times 0.8 \text{ s} = 272 \text{ m}$$
• The correct answer is (a) 272m.

Question 24: An optical instrument that uses a converging lens to form a real image is

• A camera uses a converging lens to form a real image on a film or sensor.
• The correct answer is (d) camera.

Question 25: ______ collects and focuses light.

• A lens is the component specifically designed to collect and focus light.
• The correct answer is (b) Lens.

Question 26: ______ records the image.

• In a traditional camera, the film records the image formed by the lens.
• The correct answer is (a) Film.