The refractive index of glass is 1.5 and the speed of light in air is 3 x 10^8 m/s. What is the speed of light in the glass?
Answer and explanation
Correct answer: C. 2 x 10^8 m/s
- Step 1: Refractive index = speed in air / speed in glass. Step 2. Speed in glass = 3 x 10^8 / 1.5 = 2 x 10^8 m/s. Answer: 2 x 10^8 m/s. Why not the others: 4.5 x 10^8 m/s: That multiplies by the index, but light is slower in glass. 1.5 x 10^8 m/s: That halves the speed in air. 3 x 10^8 m/s: That is the speed in air.
Practise more Heat, light and waves.
Free questions with an explanation for every one, and full timed Kenya KCSE mock tests.
More Heat, light and waves questions
- What energy is needed to raise the temperature of 2 kg of water by 10 degrees Celsius? (specific heat capacity of water = 4200 J/kg per degr…
- How is heat transferred through a vacuum?
- A steel rod 2.0 m long is heated and its temperature rises by 100 degrees Celsius. If the linear expansivity of steel is 0.000012 per degree…
- An object is placed 30 cm in front of a plane mirror. How far is the image from the object?
- The speed of a wave of frequency 50 Hz and wavelength 6 m is
- A ray of light passes from air into glass. Which statement is correct?