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#chromatic aberration

3 public questions tagged with this topic.

Optical Instruments - Simple and Compound Microscope

Why does the image in a reflecting telescope remain free of chromatic aberration?

**Compound microscope** M = m_o × M_e, objective magnification m_o = v_o/u_o ≈ L/f_o, L tube length, eyepiece M_e = 1+D/f_e (image at D) or D/f_e (infinity). Objective forms real inverted magnified image at focal plane of eyepiece, eyepiece acts as simple microscope magnifying it. A reflecting telescope uses mirrors instead of lenses as the objective. Mirrors reflect all wavelengths of light uniformly, avoiding the wavelength-dependent refraction that causes chromatic aberration in lenses, resulting in a clearer, color-corrected image. Substituting values gives Due to uniform reflection of all

Ref: NCERT > Physics Book > Ray Optics > Optical Instruments - Simple and Compound Microscope

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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 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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