Multiple Choice QuestionsAn observer looks at a distant tree of height 10 m with a telescope of magnifying power of 20. To the observer the tree appears:
10 times taller.
10 times nearer.
20 times taller.
20 times taller.
C.
20 times taller.
The height of image depends upon magnifying rows to see 20 times taller object, angular magnification should be 20 and we observe angular magnification option (c) would not be very correct as the telescope can be adjusted to form the image anywhere between infinity and least distance for distinct vision.Suppose that the image is formed at infinity. Then. the observer will have to focus the eyes at infinity to observe the image. Hence, it is incorrect to say that the image will appear nearer to the observer.
The box of a pinhole camera, of length L, has a hole of radius a. It is assumed that when the hole is illuminated by a parallel beam of light of wavelength λ the spread of the spot (obtained on the opposite wall of the camera) is the sum of its geometrical spread and the spread due to diffraction. The spot would then have its minimum size (say bmin) when:
Radiation of wavelength λ is incident on a photocell. The fastest emitted electron has to speed v. If the wavelength is changed to 3λ/4, the speed of the fastest emitted electron will be:
= v(4/3)1/2
= v(4/3)1/2
Half-lives of two radioactive elements A and B are 20 minutes and 40 minutes, respectively. Initially, the samples have equal number of nuclei. After 80 minutes, the ratio of decayed numbers of A and B nuclei will be:
1: 16
4 : 1
1: 4
1: 4
If a, b, c, d are inputs to a gate and x is its output, then, as per the following time graph, the gate is:
NOT
AND
OR
OR
Choose the correct statement:
In amplitude modulation, the amplitude of the high-frequency carrier wave is made to vary in proportion to the amplitude of the audio signal.
In amplitude modulation, the frequency of the high-frequency carrier wave is made to vary in proportion to the amplitude of the audio signal.
In frequency modulation, the amplitude of the high-frequency carrier wave is made to vary in proportion to the amplitude of the audio signal.
In frequency modulation, the amplitude of the high-frequency carrier wave is made to vary in proportion to the amplitude of the audio signal.
A pipe open at both ends has a fundamental frequency f in the air. The pipe is dipped vertically in water so that half of it is in water. The fundamental frequency of the air column is now:
f/2
3f/4
2f
2f
In an experiment for determination of refractive index of glass of a prism by i− δ, plot, it was found that a ray incident at angle 35o, suffers a deviation of 408 and that it emerges at angle 79o ⋅ Ιn that case which of the following is closest to the maximum possible value of the refractive index?
1.5
1.6
1.7
1.7
Identify the semiconductor devices whose characteristics are given below, in the order (a), (b), (c), (d):
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