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Lens formula

1/f = 1/v − 1/u

Where: f = frequency (Hz) / focal length (m), u = initial velocity (m/s), v = final velocity / speed (m/s)

Solved example

Given: u = 7, v = 5
Find: f (frequency (Hz) / focal length (m))

  1. Formula: 1/f = 1/v - 1/u
  2. Rearranged for f: f = u·v/(u - v)
  3. Substitute the values: f = 5·7/(-5 + 7)
  4. Result: f = 17.5

Answer: f = 17.5

Calculator

How to calculate Lens formula

  1. Write down the formula: 1/f = 1/v − 1/u.
  2. Note the known values (u, v).
  3. Substitute them and simplify to find f.
  4. Use the calculator above to solve for any letter.

Frequently asked questions

What is the formula for Lens formula?

The formula is 1/f = 1/v − 1/u, where f = frequency (Hz) / focal length (m), u = initial velocity (m/s), v = final velocity / speed (m/s).

What is Lens formula when u = 7, v = 5?

f = 17.5. Substitute the values into 1/f = 1/v − 1/u and simplify.

All Optics formulas

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