The answer is: none of the above.
Explanation:
When light reflects from a surface, the frequency, wavelength, and speed do not change. They remain the same.
12. The answer would be C. 1.50 s. This is because if you divide 60 by 40, you will get 1.5.
13. For this one I'm not sure, but what I can tell you is that the heavier something is the faster it will sink, the lighter it is, it will float.
Answer:
D
Explanation:
From the information given:
The angular speed for the block 
Disk radius (r) = 0.2 m
The block Initial velocity is:

Change in the block's angular speed is:

However, on the disk, moment of inertIa is:

The time t = 10s
∴
Frictional torques by the wall on the disk is:

Finally, the frictional force is calculated as:

