The lens equation relates the object distance, image distance, and the focal length of a lens, expressed mathematically as $$\frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i}$$. This equation is crucial in understanding how light is bent by lenses, which is particularly important in the study of gravitational lensing where massive objects like galaxies can bend light from distant sources.
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