Ultrasonic
Ultra–violet rays
Microwave technique
X–rays
Recoil of gun is an example of
Red is used as an emergency or danger signal as
Red light is used for signals as it has
Refraction of star light through the earth’s atmosphere causes
Refractive Index of glass with respect to water is
Refrigerators keep food unspoiled as
Relative humidity is expressed as
Remote-sensing device has an inbuilt source of
Richter scale is used for measuring
Rise of oil a wick is due to
