A double-concave (thickest at the edges, thinnest in the middle) thin lens is made of glass with an index of refraction of 1.6. The radius of curvature of the left and right faces of the lens are 65 cm and 75 cm, respectively. The object lies to the left of the lens. What is the focal length of the lens

Research and discuss the aurora borealis in terms of electric charges, magnetic fields, and forces. which times of the year are best for seeing the northern lights, and where are the best places to view them? explain your answers. also identify links to good images. if you’ve ever seen the aurora borealis, describe your experience and note the time and place that you saw it.