Which equation expresses the relationship between speed, frequency and wavelength?

Which equation expresses the relationship between speed, frequency and wavelength?

• A. v = f / λ
• B. v = f λ
• C. f = v × λ
• D. λ = f / v

Answer: (B)

Speed, frequency and wavelength are linked because speed is distance per unit time, frequency is how many cycles pass each second, and each cycle spans one wavelength. So the total distance traveled each second is (cycles per second) × (distance per cycle) = f × λ. That makes v = fλ the direct way to relate the three quantities, with the units lining up: Hz (s^-1) times meters gives meters per second. For a given medium, the speed v is fixed, so changing f forces λ to change inversely to keep v the same. For example, doubling the frequency means the wavelength must halve to maintain the same speed. Other forms would not give speed in meters per second and don’t match how frequency and wavelength combine to produce distance per unit time, so they aren’t correct relationships. The proper equation is v = fλ.

Speed, frequency and wavelength are linked because speed is distance per unit time, frequency is how many cycles pass each second, and each cycle spans one wavelength. So the total distance traveled each second is (cycles per second) × (distance per cycle) = f × λ. That makes v = fλ the direct way to relate the three quantities, with the units lining up: Hz (s^-1) times meters gives meters per second.

For a given medium, the speed v is fixed, so changing f forces λ to change inversely to keep v the same. For example, doubling the frequency means the wavelength must halve to maintain the same speed.

Other forms would not give speed in meters per second and don’t match how frequency and wavelength combine to produce distance per unit time, so they aren’t correct relationships. The proper equation is v = fλ.