Question

The frequency response curve (figure) for the filter circuit used for the production of AM wave should be

(A) Followed by (i)
(B) Followed by (ii)
(C) Followed by (iii)
(D) Followed by (iv)

Answer 1

Hint :In order to solve this question, we must know what a bandpass filter is, how it works, what are its functions. The definition of the frequency curve is considered and also it is drawn for the bandpass filter. The one that matches the options is the correct one.

Complete Step By Step Answer:
A bandpass filter is a device that allows frequencies within a specific range and rejects in other words, attenuated the frequencies in other ranges. The low pass filters are used specially to eliminate the frequencies higher than the cutoff frequency.
So, the basic function of the bandpass filter is to eliminate the unwanted frequencies. The frequency response of any given circuit is the variation in its behavior with changes in the input signal frequency as it shows the band of frequencies over which the output and the gain remains fairly constant.
The frequency response curve for the filter circuit used for the production of AM waves. Thus fig. (iii) is also correct and fig (i) followed by (ii) is correct.

Note :
The gain of the band pass filter first increases with increase in the angular frequency within the bandwidth and when it reaches the angular frequency $ {\omega _c} + {\omega _m} $ , the gain begins to decrease up to a point and becomes constant after that point. Thus, it allows only certain frequencies and not all of them.