Short Answer Typei) Suggest one way, by which we can detect the presence of:
1. Infrared radiation
2. Ultraviolet radiations
ii) Give one use of infrared radiations.i) 1. Infrared Radiations: Mercury rises rapidly is a blackened bulb thermometer is kept in these radiations.
2. Ultraviolet Radiations: By their chemical activity on dyes.
ii) Use of infrared radiations: Used for the therapeutic purpose by doctors.
When acoustic resonance takes place, a loud sound is heard. Why does this happen? Explain?
i) Three musical instruments give out notes at the frequencies listed below; Flute: 400 Hz; Guitar: 200 Hz; Trumpet: 500 Hz. Which one of these has the highest pitch?
ii) With which of the following frequencies does a tuning fork of 256 Hz resonates? 288 Hz, 314 Hz, 333 Hz, 512 Hz.
i) Name the type of waves which are used for sound ranging.
ii) Why are these waves mentioned in i) above, not audible to us?
iii) Give one use of sound ranging.A man standing 25 m away from a wall produces a sound and receives the reflected sound.
i) Calculate the time after which he receives the reflected sound if the speed of sound in air is 350 m/s.
ii) Will the man be able to hear a distant echo? Give a reason for your answer.i) Draw a graph of potential difference (V) versus Current (I) for an ohmic resistor.
ii) How can you find the resistance of the resistor from this graph?
iii) What is a non-ohmic resistor?i) An electric bulb is marked 100 w, 250 V. What information does this convey?
ii) How much current will the bulb draw if connected to a 250 V supply?i) Name two safety devices which are connected to the live wire of a household electric circuit.
ii) Give one important function of each of these two devices.
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