Consider the following statements : The principle of total internal reflection is applicable to explain the : 1. formation of mirage in desert. 2. formation of image in microscope. 3. colour of evening sky. 4. operation of optical fibers. Which of the statements given above are correct?

Total Internal Reflection (TIR) occurs when light travels from a denser to a rarer medium at an angle exceeding the critical angle. Statement 1 is correct as mirages are optical illusions formed when light from the sky or distant objects undergoes TIR due to temperature-induced refractive index gradients in air layers [t2][t5][t10]. Statement 4 is also correct because optical fibers utilize TIR to transmit light signals through a core-cladding structure with minimal loss [t1][t2][t5]. Statement 2 is incorrect because microscopes primarily rely on refraction through lenses to form images [c2][c4][t1]. Statement 3 is incorrect because the evening sky's color is caused by Rayleigh scattering, where shorter wavelengths are scattered away, leaving longer red/orange wavelengths [t1][t9]. Therefore, only statements 1 and 4 are correct.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > 9.3.4 Image Formation by Lenses > p. 152
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > 9.3.5 Image Formation in Lenses Using Ray Diagrams > p. 153
3. [3] https://en.wikipedia.org/wiki/Optics