# Wave Optics Notes, Class 12 Physics | SwaVid Wave Optics: NCERT Class 12 Physics notes with key ideas, formulas, common mistakes and 3 quick checks with worked answers. Written by SwaVid from the textbook. Canonical: https://www.swavid.com/cbse/class-12/physics/chapter/wave-optics Source: https://www.swavid.com/cbse/class-12/physics/chapter/wave-optics # Wave Optics ## Formulas and definitions ## Key ideas ## Common mistakes ## Quick checks ## Keep going ## Questions parents ask ## Class 12 Physics on SwaVid ### Huygens principle ### Reflection and refraction of waves ### Coherent sources and interference ### Young's double slit experiment ### Diffraction at a single slit ### Next chapter ### Related chapter ### Related chapter ### All chapters SwaVid › CBSE › Class 12 › Physics › Wave Optics Notes written by SwaVid from the NCERT textbook. Class 12 Physics, Chapter 10. Key ideas, formulas and common mistakes. CBSE prints 18 marks for Units V-VI together, not for this chapter alone. Short answer. This chapter treats light as a wave phenomenon, explaining how wave fronts propagate and bend. It establishes the principles of Huygens, interference through Young's double slit experiment, and single slit diffraction. Source: NCERT Physics Part II (Reprint 2026-27) , Chapter 10, Wave Optics A wavefront is a surface of constant phase. Each point on a primary wavefront acts as a source of secondary spherical wavelets, and the forward envelope gives the new wavefront. Huygens principle proves the law of reflection and Snell's law. When a wave enters a denser medium, its speed and wavelength decrease, but its frequency remains unchanged. Two sources are coherent if they maintain a constant phase difference over time. Superposition of waves from two coherent sources creates a sustained pattern of bright and dark fringes. Two narrow slits separated by a small distance produce an alternating series of bright and dark fringes on a distant screen. All bright and dark fringes have an equal spacing called the fringe width. When light passes through a slit of width comparable to its wavelength, it spreads into the geometrical shadow. This forms a broad central maximum flanked by secondary maxima of rapidly decreasing intensity. Try each question first. Then tap it to see the answer. β = (λ × D) / d β = (600 × 10⁻⁹ m × 1.0 m) / (0.5 × 10⁻³ m) β = 1.2 × 10⁻³ m 1.2 mm 2 θ = (2 × λ) / a 2 θ = (2 × 500 × 10⁻⁹ m) / (0.1 × 10⁻³ m) 2 θ = 1.0 × 10⁻² rad 0.01 rad λ' = λ / n λ' = 600 nm / 1.5 λ' = 400 nm 400 nm Dual Nature of Radiation and Matter . Ray Optics and Optical Instruments . Electromagnetic Waves . The 14 chapters of Class 12 Physics . CBSE does not give marks to one chapter. It prints 18 marks for Units V-VI together (Electromagnetic Waves; Optics). Wave Optics is part of that group. No. They are written by SwaVid from the NCERT textbook. The CBSE curriculum is the reference for what is assessed. Dual Nature of Radiation and Matter. SwaVid is an AI tutor for Indian students in Classes 6 to 12. It finds the earlier ideas a child missed, then teaches today’s chapter. Start free to see how it works. - Ch 10 NCERT book - 18 marks, Units V-VI together - 3 quick checks - Swapping the condition for minima between interference and diffraction . In interference, a path difference of n λ gives a maximum. In single-slit diffraction, a sin θ = n λ gives a minimum because wavelets from different halves of the slit cancel out. - Changing the frequency of light when it enters a new medium . Frequency is a characteristic of the source and never changes across boundaries. Only speed and wavelength change according to the refractive index of the medium. - Assuming diffraction fringes have uniform width and intensity . Only interference fringes have equal width and equal brightness. In diffraction, the central maximum is twice as wide as the secondary maxima, and intensity falls rapidly with order. ## Key Links - [CBSE](https://www.swavid.com/cbse) - [Class 12](https://www.swavid.com/cbse/class-12) - [Physics](https://www.swavid.com/cbse/class-12/physics/chapters) - [Start free →](https://www.swavid.com/signup) - [All 14 chapters](https://www.swavid.com/cbse/class-12/physics/chapters) - [NCERT Physics Part II (Reprint 2026-27)](https://ncert.nic.in/textbook.php?leph2=0-6) - [Open notes](https://www.swavid.com/cbse/class-12/physics/chapter/dual-nature-of-radiation-and-matter) - [Open notes](https://www.swavid.com/cbse/class-12/physics/chapter/ray-optics-and-optical-instruments) - [Open notes](https://www.swavid.com/cbse/class-12/physics/chapter/electromagnetic-waves) - [Class 12 Physics](https://www.swavid.com/cbse/class-12/physics/chapters) - [Start free →](https://www.swavid.com/signup)