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#white light

3 public questions tagged with this topic.

Total Internal Reflection and Critical Angle

Why does a convex lens produce chromatic aberration when used with white light?

**TIR application** requires n₁>n₂ and θ₁>C. Critical angle formula derived from Snell's law with θ₂=90°, n₁ sinC = n₂ sin90° = n₂, so sinC = n₂/n₁. For glass-air sinC=1/1.52, C≈41°, for water-air 48.6°, determining cutoff for transmission. Chromatic aberration occurs in a convex lens because different wavelengths of white light refract by different amounts due to the lens material’s varying refractive index for each wavelength. Shorter wavelengths (e.g., blue) focus closer than longer ones (e.g., red), causing color fringing. Substituting values gives Due to wavelength-dependent refraction, w

Ref: NCERT > Physics Book > Ray Optics > Total Internal Reflection and Critical Angle

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Refraction Through Prism and Minimum Deviation

Why does a prism disperse white light into a spectrum of colors?

**Refraction through prism** deviation δ = i+e-A, minimum when i=e, symmetrical path, r₁=r₂=A/2, n = sin[(A+δ_m)/2]/sin(A/2). In water n_rel = n_prism/n_water =1.5/1.33=1.128, so δ_m reduces because relative index lower, new δ_m from formula with n_rel. A prism disperses white light because different wavelengths (colors) of light have different refractive indices in the prism material. Shorter wavelengths (e.g., violet) refract more than longer wavelengths (e.g., red), causing the light to split into a spectrum as it exits the prism. Substituting values gives Due to different refractive indice

Ref: NCERT > Physics Book > Ray Optics > Refraction Through Prism and Minimum Deviation

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Refraction at Plane Surfaces and Snell's Law

Why does a convex lens fail to form a sharp image when used with white light unless corrected?

**Refractive index** n = c/v, water 1.33 means light 1.33 times slower than vacuum. Passing from water to air at 49°, n₁ sinθ₁ =1.33×sin49°≈1.33×0.755=1.004>1, so sinθ₂>1 impossible, total internal reflection occurs, no refraction. A convex lens exhibits chromatic aberration with white light because different wavelengths refract by varying amounts due to the lens’s material having a wavelength-dependent refractive index. This causes colored fringes as focal points differ for each color, blurring the image. Substituting values gives Due to chromatic aberration, which matches expected image posi

Ref: NCERT > Physics Book > Ray Optics > Refraction at Plane Surfaces and Snell's Law

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