Video Transcript
The lines shown in the following graph represent the spectra of light emitted by two objects. Which line represents the object for which the light emitted most brightly has a longer wavelength? (A) The red solid line, (B) the green dashed line, (C) the light emitted most brightly is at the same wavelength for both lines.
Our graph, we see, shows intensity of light emitted by two different objects against the wavelength of that light. Since there are two objects emitting light, we have two curves. One is the green dashed line, and the other the red solid line. We want to pick which of these two lines represents the object for which light emitted most brightly has a longer wavelength. The brightness of emitted light is indicated by the intensity of that light. The maximum value of intensity for our two curves will correspond to the wavelength at which the light from that object is brightest.
We see that for both of our curves, that maximum value of intensity occurs right here. These peaks overlap, and they correspond to light at this wavelength, whatever that wavelength is. The important point is that since these two peaks occur at the same wavelength, we can’t say that either one of them individually has a longer wavelength than the other. For our answer then, we’ll choose option (C). The light emitted most brightly is at the same wavelength for both lines.
