Answer:
1) The matter absorbs or reflects the light
2) Lens
3) <u><em>Concave</em></u>- curves inwards. Diverges light
b.<u><em>Convex</em></u>- curves outward. Converges light
4) The image is real if the distance of the object from the lens is greater than the focal length and virtual if it is less than the focal length
5) Lens and, for convex lenses, on the distance between the lens and the object.
6) Index of refraction?
Explanation:
I hope this helped you, sorry if anything is wrong
A. The cliff was 30.7 m high
B. I also got 9.5 as the horizontal distance
Here is my work, I find making charts like this one to find knowns and unknowns can be helpful