Light & Sound Basic Viva Questions
Light & Sound Basic Viva Questions, Short Answer Type Questions on Light and Sound, Television Engineering Viva Questions, Engineering Viva Questions
Short Answer Type Questions
Q.1. Why picture frames frequency is 25 per second in India and 30 per second in the USA?
Ans. 25 is an exact submultiple of electric mains frequency in India and 30 is an exact submultiple of electric mains frequency in the USA.
Q.2. Why green, red and blue are called primary colours?
Ans. Red, blue and green is called primary colours because all other colours can be formed by additive mixing of these three colours.
Q.3. What types of mixing occur (i) information of an image of an object on the target plate. (ii) in the picture being seen at the screen of the colour picture tube.
Ans. (1) Subtractive mixing. Image is formed by subtracting some colours from the incident white light. (ii) Additive mixing. Colours from phosphor glows reach the eye directly without any subtraction and therefore they add.
Q.4. Why are purple colours called non-spectral colours?
Ans. Purple colours are the mixtures of red and blue which are at extremes of the visible spectrum. Due to this reason, they are not visible in the rainbow or spectroscope and are called non-spectral colours.
Q.5. Why is a luminance signal transmitted in a colour system?
Ans. The luminance signal is transmitted in a colour TV system to enable a monochrome receiver to receive colour transmission as a black and white picture.
Q.6. What do you understand by red gun?
Ans. Red gun in TV terminology means the electrons gun in the picture tube which produces sharply focussed electrons beam whose strength is proportional to the intensity of red light in the original picture.
Q.7. What is the difference between tonal gradation and contrast?
Ans. Tonal gradation pertains to variation of brightness from pixel to pixel, while contrast shows variations of brightness in individual pixels over the background brightness.
Q.8. What is PMPO?
Ans. PMPO is the peak music power output that an amplifier can withstand for a moment only to reproduce the loudest tone generated by instrumentalists for a moment.
Q.9. What’s the difference between conventional stereo and surround sound?
Ans. Conventional stereo system senate direction of sound originating from two sides of the stage, left and right. The surround sound system senses the direction of sound reflected from the walls and ceiling in addition to the left and right sides of the stage.
Q.10. Why is a loudspeaker sometimes called a reverse transducer?
Ans. Conventionally any device which converts one form of energy into another form is called a transducer. but more popularly a device that converts a physical phenomenon into an electrical signal is called a transducer and one which converts electrical energy into physical form is called a reverse transducer. Hence Loudspeaker is sometimes called a reverse transducer.