Mirrors Formula

The Formula

\frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i}

When to use: A mirror sends light back in a predictable way, so your eye traces the rays and sees an image.

Quick Example

A plane mirror forms an upright virtual image, while a concave makeup mirror can magnify your face when held close.

Notation

f is focal length, d_o is object distance, d_i is image distance, and m is magnification.

What This Formula Means

Mirrors are reflective surfaces that form images by reflection. Physics courses usually study plane mirrors and curved mirrors such as concave and convex mirrors.

A mirror sends light back in a predictable way, so your eye traces the rays and sees an image.

Formal View

For spherical mirrors, the mirror equation is 1/f = 1/d_o + 1/d_i, and magnification is m = -d_i/d_o = h_i/h_o.

Common Mistakes

  • Mixing up real and virtual images.
  • Using object distance and image distance with the wrong sign convention.

Why This Formula Matters

Mirror physics appears in everyday mirrors, telescopes, headlights, and many geometric-optics problems in school curricula.

Frequently Asked Questions

What is the Mirrors formula?

Mirrors are reflective surfaces that form images by reflection. Physics courses usually study plane mirrors and curved mirrors such as concave and convex mirrors.

How do you use the Mirrors formula?

A mirror sends light back in a predictable way, so your eye traces the rays and sees an image.

What do the symbols mean in the Mirrors formula?

f is focal length, d_o is object distance, d_i is image distance, and m is magnification.

Why is the Mirrors formula important in Physics?

Mirror physics appears in everyday mirrors, telescopes, headlights, and many geometric-optics problems in school curricula.

What do students get wrong about Mirrors?

A virtual image is seen but cannot be projected onto a screen.

What should I learn before the Mirrors formula?

Before studying the Mirrors formula, you should understand: reflection.

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