Physics

An illuminated object lies at a distance 1.0 m from a screen. A convex lens is used to form the image of object on a screen placed at distance 75 cm from the lens. Find: (i) the focal length of lens, and (ii) the magnification.

Solution: According to the question, Image distance is v = 75 cm Object distance is u = -25 cm The expression for Lens formula is - 1 / v – 1 / u = 1 / f Upon substituting values, we get 1 / f = 1 /...

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In figure A, B, C and D represent the test tubes each of height 20 cm which are filled with water up to heights of 12 cm, 14 cm, 16 cm and 18 cm respectively. If a vibrating tuning fork is placed over the mouth of test tube D, a loud sound is heard.
(a) Describe the observations with the tubes A, B and C when the vibrating tuning fork is placed over the mouth of these tubes.
(b) Give the reason for your observation in each tube.
(c) State the principle illustrated by the above experiment.

(a) The tubes A and C produce no loud sound, while the tube B produces a loud sound. (b) The frequency of the air column in tube D is the same as the tuning fork's frequency. Tube B has a resonance...

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In figure A, B, C and D are the four pendulums suspended from the same elastic string XY. The lengths of pendulum A and D are equal, while the length of pendulum B is shorter and of the pendulum C is longer. The pendulum A is set into vibrations.
(a) What is your observation about the vibrations of pendulum D?
(b) Give reason for your observation in part (a).
(c) What type of vibrations take place in pendulums B and C?
(d) Give reason for the answer in part (c)

Set the pendulum A into oscillation by moving it to one side, normal to its length. It is noticed that pendulum D begins vibrating with a tiny amplitude and eventually attains the same amplitude as...

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Figure shows two tuning forks A and B of the same frequency mounted on two separate sound boxes with their open ends facing each other. The fork A is set into vibration. (a) Describe your observation. (b) State the principle illustrated by this experiment.

The vibrating tuning fork A produces forced vibrations in the air column of its soundbox. The vibrations in the soundbox have a significant amplitude due to the huge surface area of air in the...

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The diagram in figure shows the displacement-time graph of a vibrating body.
(i) Name the kind of vibrations.
(ii) Give one example of such vibration.
(iii) Why is the amplitude of vibrations gradually decreasing?
(iv) What happens to the vibrations of the body after some time?

(i) Vibrations that have been dampened(ii) Example: When a tuning fork is stroked on a rubber pad, it produces damped air vibrations.(iii) The frictional force reduces the amplitude of vibrations....

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The diagram below in Fig. shows three ways in which the string of an instrument can vibrate.
(a)Which of the diagram shows the principal note?
(b)Which vibration has the frequency four times that of the first?
(c) Which vibration is of longest wavelength?
(d)What is the ratio of the frequency of vibrations in the diagram (i) and (ii)?

(a) A diagram depicting the main note is (i) (b) A diagram with four times the frequency of the first is shown (iii) The diagram with the longest wavelength is shown in (c) (i) (d) The frequency of...

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A person standing at a distance x in front of a cliff fires a gun. Another person B standing behind the person A at a distance y from the cliff hears two sounds of the fired shots after 2s and 3s respectively. Calculate x and y (take speed of sound 320 m/s)

Two of the fired rounds are heard by person B; the first is straight from the gun, while the second is reflected from the cliff. Given a sound speed of 320 m/s The time it takes for sound to travel...

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A pendulum has a frequency of 5 vibrations per second. An observer starts the pendulum and fires a gun simultaneously. He hears an echo from the cliff after 8 vibrations of the pendulum. If the velocity of sound in air is 340m/s, find the distance between the cliff and the observer.

We know that, The pendulum vibrates 5 times each second. As a result, for 8 vibrations, the time is 8 / 5 seconds. similarly 2 D / time = Velocity 2 D / 1.6 = 340 This implies that...

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A man standing 25 m away from a wall produces a sound and receives the reflected sound. (a) Calculate the time after which he receives the reflected sound if the speed of sound in air is 350 m/s. (b) Will the man be able to hear a distinct echo? Explain the answer.

(a) Velocity = Time / 2D so, time= \(\frac{2\times 25}{350}\) Hence, Time = 0.143 seconds (b) The reflected sound arrives at the guy 0.1 second after the initial sound, while the original sound...

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Give a reason for the following:
(i) Infrared radiations are used for photography in fog
(ii) Infrared radiations are used for signals during the war.
(iii)The photographic darkrooms are provided with infrared lamps.
(iv)salt prism is used instead of a glass prism to obtain the infrared spectrum.
(v)A quartz prism is required for obtaining the spectrum of the ultraviolet light.
(vi)Ultraviolet bulbs have a quartz envelope instead of glass.

(i)Infrared radiations are employed for fog photography because they are less dispersed and can penetrate the fog effectively. (ii)Because infrared radiation is not visible and does not absorb well...

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