Amplitude of a Wave

Q. Define modulation index. Why is it kept low ? What is the role of a band pass filter ?

Q. In amplitude modulation, the message signal $V_m\left(t\right)=1\sin (2\pi \times {10}^{5}t)$ volts and carrier signal $V_C\left(t\right)=20\sin (2\pi \times {10}^{7}t)$ volts. The modulated signal now contains the message signal with lower side band and upper side band frequency. Therefore the bandwidth of modulated signal is $\alpha \text{kHz}$. The value of $\alpha$ is :

1. $0\text{kHz}$
2. $50\text{kHz}$
3. $200\text{kHz}$
4. $100\text{kHz}$

Q.

How do you calculate modulation?

Q.

A wire, fixed at both ends is seen to vibrate at a resonant frequency of 240 Hz and also at 320 Hz. (a) What could be the maximum value of the fundamental frequency ? (b) If transverse waves can travel on this string at a speed of $40m{s}^{-1}$, what is its length ?

Q. A carrier wave of peak voltage 15 V is used to transmit a message signal. Find the peak voltage of the modulating signal in order to have a modulation index of 60%.

Q. For amplitude modulated wave, carrier frequency should be message frequency.

1. greater than
2. equal to
3. lesser than

Q. Distinguish between modulation and demodulation.

Q. What is the difference between amplitude modulation and frequency modulation?

Q. Due to economic reasons, only the upper sideband of an AM wave is transmitted, but at the receiving station, there is a facility for generating the carrier. Show that if a device is available which can multiply two signals, then it is possible to recover the modulating signal at the receiver station.

Q. Differentiate analog signal and digital signal with diagrams.

Q. For an amplitude modulated wave, the maximum amplitude is found to be $12V$ and minimum amplitude is found to be $4V$. The modulation index of this wave is __________ %.

1. $50$
2. $75$
3. $25$
4. $20$

Q.

State three important factors showing the need for translating a low frequency signal into a high frequency wave before transmission.

Draw a sketch of a sinusoidal carrier wave along with a modulating signal and show how these are superimposed to obtain the resultant amplitude modulated wave.

Q. The process of superimposing audio or video messages on r.f. carrier waves is called modulation.

1. True
2. False

Q. In amplitude modulation, sinusoidal carrier frequency used is denoted by ${\omega }_c$ and the signal frequency is denoted by ${\omega }_m$. The bandwidth $\left(△{\omega }_m\right)$ of the signal is such that $△{\omega }_m<<{\omega }_c$. Which of the following frequencies is not contained in the modulated wave?

1. ${\omega }_c-{\omega }_m$
2. ${\omega }_m$
3. ${\omega }_c$
4. ${\omega }_m+{\omega }_c$

Q. A technique used by codes to convert an analog signal into a digital bit stream is known as __________.

1. Pulse code modulation
2. Pulse stretcher
3. Query processing
4. None of the above
5. Queue management

Q. Derive expression for amplitude modulated wave? What is meant by side band frequencies in carrier wave?

Q. is there any method to remember the wavelength and frequency of EM WAVES ?

Q.

The process of impressing any information by changing the original signal is called

Q. When signal amplitude is equal to the carrier wave amplitude, then the modulation factor is

1. $2$
2. $1/4$
3. $1$
4. $1/2$

Q. In the half wave rectifier circuit operating from $50Hz$ mains frequency, the fundamental frequency in the ripple would be

1. $50Hz$
2. $100Hz$
3. $70.7Hz$
4. $25Hz$

Q. Write two basic modes of communication. Explain the process of amplitude modulation. Draw a schematic sketch showing how amplitude modulated signal is obtained by superposing a modulating signal over a sinusoidal carrier wave.

Q.

explain in detail about the radio waves and how they are transmitted through very large distances for communication?

Q. Which of the following performs modulation and demodulation

1. Fiber optic
2. Satellite
3. Modem
4. Coaxial cable

Q. Define modulation index. Why is it's value kept, in practice, less than one?
A carrier wave of frequency 1.5 MHz and amplitude 50 V is modulated by a sinusoidal wave of frequency 10 kHz producing 50% amplitude modulation. Calculate the amplitude of the AM wave and frequencies of the side bands produced.

Q. Due to economic reasons, only the upper side band of an AM wave is transmitted, but at the receiving station, there is a facility for generating the carrier. Show that if a device is available which can multiply two signals, then it is possible to recover the modulating signal at the receiver station.

Q. The ratio of $E_{max}-E_{min}$ to $E_{max}+E_{min}$ is known as

1. Amplitude variation of modulating signal
2. Range of modulating signal
3. Depth of modulation
4. Frequency of modulation

Q. For television transmission, the range of carrier waves is approximately ......................

1. 300 kHz to 300 MHz
2. 100 kHz to 30 MHz
3. None of the above
4. 30 MHz to 300 MHz

Q. What remains constant in an amplitude modulation?

1. Amplitude
2. Frequency
3. Phase
4. Pulse

Q.

Due to economic reasons, only the upper sideband of an AM wave is transmitted, but at the receiving station, there is a facility for generating the carrier. Show that if a device is available which can multiply two signals, then it is possible to recover the modulating signal at the receiver station.

Q.

A carrier wave of peak voltage 12 V is used to transmit a message signal. What should be the peak voltage of the modulating signal in order to have a modulation index of 75%?