Consider the following statements: 1. Light of longer wavelength is scattered much more than the light of shorter wavelength. 2. The speed of visible light in water is 0.95 times and speed in vacuum. 3. Radio waves are produced by rapidly oscillating electrical currents. 4. To detect the over speeding vehicles, police use the Doppler effect of reflected short radio waves Which of these statements are correct ?

Statement 1 is false: Rayleigh scattering causes shorter (blue) wavelengths to be scattered more strongly than longer (red) wavelengths [1]. Statement 2 is false: the speed of light reduces considerably in water compared to vacuum; a value of 0.95c is not consistent with the substantial reduction in speed on entering water (refractive-index effect) [2]. Statement 3 is true: radio waves arise from oscillating charges/currents — electrons vibrating and re-radiating energy produce radio emission [3]. Statement 4 is true: police radar uses the Doppler shift of reflected short radio/microwave waves to determine vehicle speed (Doppler principle applied to reflected radio waves).

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 10: The Human Eye and the Colourful World > 10.6.2 Why is the colour of the clear Sky Blue? > p. 169
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > 9.3.2 The Refractive Index > p. 148
3. [3] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 20: Earths Atmosphere > Explanation: > p. 279