An object is located 20.0 cm from a convex lens. The lens focuses light at a distance of 10.0 cm. What is the image distance?

A. 6.67 cm
B. -6.67 cm
C. -20.0 cm
D. 20.0 cm

The Answer Is :  D. 20.0 cm

My Reason : These types of problems can all be solved using the lens or mirror equation.

1/20 +1/q= 1/10

q=20 cm

The image is formed behind the lens at 2f or the center of curvature.

It is real, inverted, and the same size as the object

c.the charges if the proton and electron and gravity

answer: 802.3 kilo joules of energy represents 191.75 kilo calorie of energy.

explanation:

energy released during combustion of one mole methane = 802.3 kilo joules

if 1 kilo joule = 0.239006   kilo calorie

then ,802.3 kilo joule will be = 802.30.239006 kilo calorie

802.3 kilo joule = 191.75 kilo calorie

hence, the energy in kilo calorie is 191.75 kilo calorie.