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Physics · Grades 11–12

Photon energy in a scaled unit

Track powers of ten; the answer is a coefficient in units of 10⁻¹⁹ J.

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Rule and assumptions

Track powers of ten; the answer is a coefficient in units of 10⁻¹⁹ J.

E = hf

Worked examples

A photon has frequency 15 × 10¹⁴ Hz. Use h = 6.63 × 10⁻³⁴ J·s. Write E = a × 10⁻¹⁹ J and find a. Round to 3 decimal places if needed.

E = hf (6.63 × 15) × 10^(−34 + 14 + 19) = 9.945

9.945

A photon has frequency 5.2 × 10¹⁴ Hz. Use h = 6.63 × 10⁻³⁴ J·s. Write E = a × 10⁻¹⁹ J and find a. Round to 3 decimal places if needed.

E = hf (6.63 × 5.2) × 10^(−34 + 14 + 19) = 3.448

3.448

Try two questions

  1. A photon has frequency 5.5 × 10¹⁴ Hz. Use h = 6.63 × 10⁻³⁴ J·s. Write E = a × 10⁻¹⁹ J and find a. Round to 3 decimal places if needed.

  2. A photon has frequency 14.7 × 10¹⁴ Hz. Use h = 6.63 × 10⁻³⁴ J·s. Write E = a × 10⁻¹⁹ J and find a. Round to 3 decimal places if needed.

Answers and reasoning

Answers and marking notes
  1. 3.647

    E = hf (6.63 × 5.5) × 10^(−34 + 14 + 19) = 3.647

  2. 9.746

    E = hf (6.63 × 14.7) × 10^(−34 + 14 + 19) = 9.746

Further reading and review references

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Learning preview · independent educational and translation review required. Suggested grades are not official curriculum alignment.