D) The speed of a wave slows as it travels at different speed in different media.
Answer:
B
Explanation:
Gravitational Energy is the energy of position or place. A rock resting at the top of a hill contains gravitational Potential energy. Hydropower, such as water in a reservoir behind a dam, is an example of gravitational potential energy.
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Answer:
Resistance in the flash tube, 
Explanation:
It is given that,
Speed of the bullet, v = 500 m/s
Distance between one RC constant, d = 1 mm = 0.001 m
Capacitance, 
The time constant of RC circuit is given by :

R is the resistance in the flash tube
..........(1)
Speed of the bullet is given by total distance divided by total time taken as :




Equation (1) becomes :


So, the resistance in the flash tube is
. Hence, this is the required solution.