Total Internal Reflection (TIR)

Detailed Notes - Toppers’ Perspective

1. Critical Angle ( NCERT: Physics, Class 12, Chapter 9: Ray Optics and Optical Instruments )

• The critical angle is the angle of incidence beyond which light undergoes total internal reflection, meaning it is entirely reflected back into the denser medium.

• Formula for critical angle: sinθc = n2/n1, where θc is the critical angle, n1 is the refractive index of the denser medium, and n2 is the refractive index of the rarer medium.

2. Laws of Refraction ( NCERT: Physics, Class 12, Chapter 9: Ray Optics and Optical Instruments )

• Snell’s law of refraction states that the ratio of the sine of the angle of incidence (i) to the sine of the angle of refraction (r) is equal to the refractive index (n) of the second medium relative to the first medium: sin i / sin r = n2/n1.

• Use Snell’s law to calculate the critical angle by setting the angle of refraction to 90 degrees (total internal reflection).

3. Total Internal Reflection in Prisms ( NCERT: Physics, Class 12, Chapter 9: Ray Optics and Optical Instruments )

• Total internal reflection occurs in a prism when light passes from a denser medium (prism) to a rarer medium (air).

• Understand the geometry of the prism and trace the path of the light rays through it, considering critical angles at each interface.

4. Applications of Total Internal Reflection ( NCERT: Physics, Class 11, Chapter 11: Optics )

• Prisms: Analyze the dispersion of light passing through a prism and the formation of a spectrum.

• Optical fibers: Study how total internal reflection enables the transmission of light over long distances with minimal loss.

• Periscopes: Investigate the design and functionality of periscopes and how they utilize total internal reflection.

5. Internal Reflection in Lenses

• Total internal reflection can occur within lenses, affecting the path of light rays and image formation.

• Investigate the effects of internal reflection on image quality and potential aberrations in lenses.

6.TIR in Optical Fiber ( NCERT: Physics, Class 12, Chapter 9: Ray Optics and Optical Instruments )

• Optical fibers employ total internal reflection to transmit light signals with high efficiency.

• Understand the concept of numerical aperture and its impact on the transmission efficiency of optical fibers.

7. Wave Nature of Light and TIR

• Relate total internal reflection to the wave nature of light, considering the interference and diffraction effects associated with its occurrence.

8. Experimental Verification of TIR

• Study and analyze experimental setups that demonstrate the laws of reflection and refraction, including demonstrations of total internal reflection.

Remember to consult NCERT textbooks and additional reference materials to enhance your understanding and proficiency in this topic. Regular practice with relevant problems and conceptual questions will help solidify your knowledge and prepare you for successful performance in the JEE exam.