Consider the following phenomena : 1. Size of the sun at dusk 2. Colour of the sun at dawn 3. Moon being visible at dawn 4. Twinkle of stars in the sky 5. Polestar being visible in the sky Which of the above are optical illusions?
Asked in UPSC IAS 2013 · Topic: Optics (Prisms and Dispersion)
More Physics questions
- The apparent increase in the size of the sun (or moon) near the horizon (dusk) is an optical illusion known as the Moon illusion. 2. The reddish/orange colour of the sun at dawn is due to atmospheric scattering (Rayleigh scattering), where shorter wavelengths (blue/green) are scattered away more than longer wavelengths (red/orange) when light travels a longer path through the atmosphere. This phenomenon leads to a perceived colour change. 4. The twinkling of stars is caused by atmospheric refraction due to turbulence in the air, which makes the light from distant stars appear to fluctuate in brightness and position. 135. Rainbow is produced when sunlight falls on drops of rain. Which of the following physical phenomena are responsible for this? 1. Dispersion 2. Refraction 3. Internal reflection Select the correct answer using the codes given below.
- ‘Red’ is used as a danger signal because
- Twinkling of stars is on account of
- 79.Red light is used for danger signals becaus it:
- Red light is used as danger signal because it
- The number of colours contained in the sunlight is
- The colour of the light is fixed by its
- Which one of the following colours is seen in the middle of a rainbow ?
