A double-concave lens has equal radii of curvature of 15.1 cm. An object placed 14.2cm from the lens forms a virtual image 5.29cm from the lens. What is the index of refraction of the lens material?
a) 1.77
b) 1.98
c) 1.82
d) 1.90 <--- Correct answer, but I do not know how to solve for it.
e) 1.04

An insulated thermos contains 148 g of water at 72.7 ˚c. you put in a 11.7 g ice cube at 0.00 ˚c to form a system of ice + original water. the specific heat of liquid water is 4190 j/kg•k; and the heat of fusion of water is 333 kj/kg. what is the net entropy change of the system from then until the system reaches the final (equilibrium) temperature?

Amother used 150 watts of power to raise a 15 newton object in a time interval of 8.0 seconds. through what vertical distance was the object raised ?

Sound travels slower in colder air that it does in warmer air. make a claim about the effect of air temperature on the speed of sound. support your claim with evidence