An object is placed 200 cm in front of a concave mirror. the image appears in the exact same location, 200 cm in front of the mirror (on top of the object itself). what is the focal length of the mirror? a. 50 cm b. 100 cm c. 200 cm d. 400 cm

The speed of light in a material is 0.50 c. what is the critical angle of a light ray at the interface between the material and a vacuum?

Hydrogen and helium are both members of?

As part of your daily workout, you lie on your back and push with your feet against a platform attached to two stiff springs arranged side by side so that they are parallel to each other. when you push the platform, you compress the springs. you do an amount of work of 79.0 j when you compress the springs a distance of 0.230 m from their uncompressed length. (a) what magnitude of force must you apply to hold the platform in this position? (b)how much additional work must you do to move the platform a distance 0.230 m farther? (c) what maximum force must you apply to move the platform a distance 0.230 m farther?