My problem is about rays traveling through a GRIN medium, where the refractive index is maximum at the center and decreases quadratically outward. Intuitively, I would expect rays starting above or below the axis to refract upward (away from the axis), since that seems like the way to minimize their own optical path length (shorter distance, lower index region). But in fact, the rays bend inward …
Tilt a CD or DVD under a desk lamp and a band of color sweeps across its surface. The disc is not painted; it is a spiral of microscopic pits, packed so tightly that they act on light the way a finely ruled scientific instrument does. Each wavelength of white light leaves the surface at its own angle, and your eye sees the result fanned out as a rainbow. That is a diffraction grating at work. The…
A new measurement method reveals that light can twist nanoscale objects in unexpected ways. Light is not just something we see. It can also exert physical forces that push and twist matter. In the 1870s, James Clerk Maxwell proposed that light carries momentum and can apply pressure to objects. Nearly 100 years later, in the [...]
