1(v)
When a blackened bulb thermometer is moved beyond the red region of the visible spectrum, there is a rapid rise in the temperature. This is due to the presence of :
- (a)Infrared radiations
- (b)Ultraviolet radiations
- (c)X-rays
- (d)Radio waves
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Infrared radiations
Reason — When a blackened bulb thermometer is placed beyond the red end of the visible spectrum, the temperature rises rapidly because this region contains infrared radiations. Infrared rays are invisible but carry significant heat energy, which is absorbed by the blackened bulb, causing the temperature to increase.
Therefore, the correct answer is Infrared radiations.