# Instrumentation Transducers Questions and Answers – Frequency Measurement

This set of Instrumentation Transducers Multiple Choice Questions & Answers (MCQs) focuses on “Frequency Measurement”.

1. Which of the following cannot be used as a unit for frequency?
a) Hz
b) BPM
c) RPM
d) S

Explanation: Frequency is a measure of repetition of a quantity over a specific time interval. S (Second) cannot be used for representing frequency. Hz or hertz is the SI unit representation of frequency, other units are Beats per minute (BPM) and Rotation per minute (RPM).

2. Which of the following represents the correct relationship between frequency and angular frequency?
a) ω=2πf
b) ω=πf
c) f=2πω
d) f=πω

Explanation: Angular frequency is the product of the frequency of a system and 2π. Frequency is represented in Hertz and angular frequency is represented in rad/sec.

3. What will be the frequency of a system in which 35 events occur in 7 seconds?
a) 7Hz
b) 35Hz
c) 5Hz
d) 10Hz

Explanation: Frequency is the number of occurrence of an event in a given time interval. That is for 35 events in 7 seconds frequency is 35÷7=5Hz.

4. Which of the following device can be used for measurement of frequency?
a) Voltmeter
b) Ammeter
c) Stroboscope
d) None of the mentioned

Explanation: Stroboscope is a frequency measuring instrument which uses another reference signal with a known frequency. Voltmeter is used for measuring voltage and Ammeter is used for measuring current.

5. All waves in electromagnetic spectrum has the same speed in vacuum.
a) True
b) False

Explanation: All waves in electromagnetic spectrum has the same speed in vacuum and their speed will be equal to speed of light c. Hence wavelength can be represented as inversely proportional to frequency.

6. Which of the following frequency range represents an audible frequency range of humans?
a) Below 20Hz
b) Between 20Hz and 20 KHz
c) Above 20 KHz
d) All of the mentioned

Explanation: Audible frequency range means, frequency of the sound signal that can hear by humans. Audible frequency range of human is recognized as between 20Hz and 20 KHz.

7. Which of the following is the correct relationship between speed of light in vacuum and frequency of light?
a) c=fλ
b) c=f
c) λ=cf
d) c=λ2

Explanation: In vacuum product of wavelength and frequency of light can be equated to speed of light, that is wavelength and frequency are inversely proportional.

8. In a dispersive medium, speed of light depends on frequency.
a) True
b) False

Explanation: Speed of light is independent on any factors only in vacuum, in a dispersive medium it may vary according to wavelength of light. Hence the inverse proportionality may not be always correct here.

9. Which of the following range represents frequency range of rainbow colors?
a) Below 4×1014Hz
b) Between 4×1014Hz and 8×1014Hz
c) Above 8×1014Hz
d) Between 0Hz and 8×1014Hz

Explanation: Colors of rainbow lies in the frequency range 4 – 8×1014Hz, in which 4×1014Hz represents frequency of red light.

10. What will be the frequency of the signal A sin (4πt+ɸ)?
a) 2Hz
b) 0.5Hz
c) 2πHz
d) 4πHz

Explanation: Frequency is the ratio of angular frequency and 2π. Here angular frequency is 4π.
Hence frequency = angular frequency ÷ 2π.

Sanfoundry Global Education & Learning Series – Instrumentation Transducers.

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