Website
NASA

Rxte Learning Center: Frequency, Wave Length, and Energy Activity

For Students 9th - 10th
Resource focuses on the relationship between the frequency, wavelength and speed of light. Has a link to an interactive activity relating frequency, wavelength, and energy.
Unit Plan
Physics Classroom

The Physics Classroom: The Wave Equation

For Students 9th - 10th
A thorough explanation of the wave equation (Speed = Wavelength * Frequency). A data table and questions to check one's understanding are also part of this lesson.