What are 3 differences and similarities between a single and double concave lenses?

Abird flies directly overhead from where you stand at an altitude of 300.0 m and at a speed horizontal to the ground of 20.0 m/s. the bird has a mass of 2.0 kg. the radius vector to the bird makes an angle \thetaθ with respect to the ground. the radius vector to the bird and its momentum vector lie in the xyxy-plane. what is the bird’s angular momentum about the point where you are standing?

In the graph, each sinusoidal curve shows the shape of a vibrating string at a different moment. for which values of x does a node occur? (let k = an integer from -2 to +2.) k + 0.5 0.5k k 2k + 1.5

Fluorine and chlorine molecules are blamed for