A Cassegrain astronomical telescope uses two mirrors to form the image. The larger (concave) objective mirror has a focal length f1 = +51.5 cm. A small convex secondary mirror is mounted d = 43.5 cm in front of the primary. As shown in the figure, light is reflected from the secondary through a hole in the center of the primary, thereby forming a real image 8.00 cm behind the primary mirror. Find the radius of curvature of the secondary mirror?

A. In order to completely melt a material,

•     Heat must be added to bring the material to the melting temperature & then the latent heat of fusion must be added to change the phase.
•     Heat must be added to make the object exp& to the melting volume
•     No heat needs to be added.
•     Stir while adding heat.

B. An aluminum rod 15 cm in length is heated from 10 degrees Celsius to 50 degrees Celcius. Find the change in length?

•     15 cm
•     8 cm
•     6 cm
•     None of the above.

C. Compute is Kepler’s first law of planetary orbits?

•     The planets move on ellipses with the Sun at the center of the ellipse.
•     The planets revolve around the Earth.
•     The position of the planets foretells the future.
•     The planets move on ellipses with the Sun at one of the foci.