To alter the wavelength of a beam of light, Jamal would need to change the medium through which the light travels. The wavelength of light is dependent on the refractive index of the medium. If Jamal wants to increase the wavelength, he can choose a medium with a higher refractive index. Conversely, if he wants to decrease the wavelength, he can choose a medium with a lower refractive index. The change in medium will cause the light to bend or refract, resulting in a change in its wavelength.
