The human eye can change the shape of its crystalline lens, and thus modify the lens strength (a. k.a., lens power) of the eye in order to bring things at different distances from the observer into sharp focus on its retina. If the total effective lens strength (a. k.a., lens power) of a human's eye at a particular moment is 53.0 D, how far from the eye is the object that is currently in focus on the retina

Ahollow metal sphere has 6 cm and 11 cm inner and outer radii, respectively. the surface charge density on the inside surface is −100nc/m2. the surface charge density on the exterior surface is:

In positive numbers less than 1, the zeros between the decimal point and non zero are significant

Imagine you are riding on a yacht in the ocean and traveling at 20 mph. you then hit a golf ball at 100 mph from the deck of the yacht. you see the ball move away from you at 100mph, while a person standing on a near by beach would observe your golf ball traveling at 120 mph (20 mph + 100 mph). now imagine you are aboard the hermes spacecraft traveling at 0.1c (1/10 the speed of light) past mars and shine a laser from the front of the ship. you would see the light traveling at c (the speed of light) away from your ship. according to einstein’s special relativity, how fast will a person on mars observe the light to be traveling? a) 0.1c (1/10 the speed of light) b) c (the speed of light) c)1.1c (c+0.1c)