Wired Faculty
When monochromatic light travels from one medium to another its wavelength changes but frequency remains the same, Explain.
When monochromatic light travels from one medium to another it’s wavelength and speed both changes and the frequency remains unchanged.
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Two convex lenses of same focal length but of aperture A1 and A2 (A2 < A1), are used as the objective lenses in two astronomical telescopes having identical eyepieces. What is the ratio of their resolving power? Which telescope will you prefer and why? Give reason.
Resolving power is given by, R = 
; where A is the aperture. 
Magnification of telescope is given by, m = 
m is same for both.
Inorder to view the finer details of the object we use telescope of high resolving power.
Therefore, telescope having convex lens aperture A1 is used
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Draw the output waveform at X, using the given inputs A and B for the logic circuit shown below. Also, identify the logic operation performed by this circuit. 
From the waveform given, we can say that 
which is the Boolean expression of OR.
The output waveform for OR gate is given by, 
Name the semiconductor device that can be used to regulate an unregulated dc power supply. With the help of I-V characteristics of this device, explain its working principle.
Zener diode can be used to regulate an unregulated dc power supply. 
Working principle of Zener diode as per the V-I characteristics:
In reverse breakdown region or zener region, a very small change in voltage across the zener diode produces very large change in current through the circuit but the voltage across the zener remains constant.
Draw the transfer characteristic curve of a base biased transistor in CE configuration. Explain clearly how the active region of the V0 versus Vi curve in a transistor is used as an amplifier.
The transfer characteristic curve of a base biased transistor in CE configuration is shown below: 
In the active region, a small increase of input voltage (Vi)results in a large increase in IC. The gradual increase in current is a linear phenomenon. This results in an increase in the voltage drop across RC.
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Mock Test Series
