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#plane mirror

6 public questions tagged with this topic.

Optical Phenomena and Applications

What is the shape of the wavefront reflected by a plane mirror when a spherical wave is incident on it?

**Convex lens focusing** plane wave into point because lens introduces phase delay proportional to thickness, converting plane wavefront to spherical converging to focal point, property ensures rays parallel to axis meet at focus, spherical aberration minimized for paraxial rays, lensmaker's formula determines focal length. A spherical wavefront incident on a plane mirror reflects as a spherical wavefront, diverging from the mirror’s virtual focus. Using Δ = d sinθ, y = n λ D/d, a sinθ = n λ, I = I₀ cos²θ, n = c/v, sinC = 1/n, λ' = λ/n and A = 2a cos(φ/2), calculation gives Spherical, illustra

Ref: NCERT > Physics Book > Wave Optics > Optical Phenomena and Applications

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Refraction at Spherical Surfaces and Lens Maker's Formula

Why is the image formed by a plane mirror always virtual?

**Lens maker's formula** 1/f = (n-1)(1/R₁ - 1/R₂), n refractive index, R₁,R₂ radii of curvature (m), sign convention R positive if surface convex towards incident light. For double convex R₁=12 cm, R₂=-12 cm, n=1.5, 1/f=(0.5)(1/12 -1/(-12))=(0.5)(2/12)=1/12, f=12 cm, converging. In a plane mirror, the reflected rays do not actually converge but appear to diverge from a point behind the mirror when traced backward. This apparent origin of rays behind the mirror results in a virtual image that cannot be projected onto a screen. Substituting values gives Due to apparent divergence from behind the

Ref: NCERT > Physics Book > Ray Optics > Refraction at Spherical Surfaces and Lens Maker's Formula

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Total Internal Reflection and Critical Angle

In a plane mirror, what property ensures that the image is not distorted?

**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. The flat surface of a plane mirror ensures that all incident rays reflect with equal angles of incidence and reflection, maintaining the object’s proportions and shape. Curved surfaces would distort the image by altering ray directions unevenly. Substituting values gives Flatness of the reflecting surface, which matches expected image position and magnifica

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

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Total Internal Reflection and Critical Angle

In a plane mirror, why does the image distance equal the object distance?

**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. In a plane mirror, light reflects such that the angle of incidence equals the angle of reflection. This symmetry ensures that the perpendicular distance from the object to the mirror equals the apparent distance of the image behind it, as the image forms along the normal extended backward. Substituting values gives Due to equal angles of incidence and refle

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

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Reflection by Spherical Mirrors and Mirror Formula

Why does a plane mirror not produce magnification greater than unity?

**Concave mirror image formation** depends on object position: beyond C real inverted diminished between F and C, at C real inverted same size at C, between C and F real inverted magnified beyond C, at F image at infinity, within F virtual erect magnified behind mirror. A plane mirror reflects light such that the image distance equals the object distance, and the image is formed by direct reflection without convergence or divergence. This results in an image of the same size as the object, with a magnification of 1, as there’s no mechanism to alter the apparent size. Substituting values gives

Ref: NCERT > Physics Book > Ray Optics > Reflection by Spherical Mirrors and Mirror Formula

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PHYSICS

What is the shape of the wavefront reflected by a plane mirror when a spherical wave is incident on it?

A spherical wavefront incident on a plane mirror reflects as a spherical wavefront, diverging from the mirror’s virtual focus. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.

Ref: NCERT Physics Textbook for Class XI and XII, Chapter: Ray Optics and Optical Instruments and Wave Optics, Topic: Refraction, lenses and interference/diffraction.

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