To form a hydrogen atom, a proton is fixed at a point and an electron is brought from far away to a distance of 0.529×10-10m, the average distance between proton and electron in a hydrogen atom. How much work is done?

How does the image distance (di) of a convex lens compare with the image distance of a concave lens? a. the image distance of the convex lens is positive, and that of the concave lens is negative. b. both are negative for a virtual image. c. both are positive for a virtual image d. the image distance of the convex lens is negative, and that of the concave lens is positive.

What are similarities and differences of reflection, refraction, diffraction and absorption?

Abucket full of water weights 4 kg and water well is 10m deep. a girl draws water from the well. it takes the girl 3 minutes to draw a bucket full of water from the well. what is the power of the girl?