Answer:
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Answer:
P = 3.5 D
Explanation:
As we know that convex lens is to be used to make the near point of eye to be correct
So we will have

here we have


now plug in all values into the formula


now for power of lens


so the power in dioptre is
P = 3.5 D
Answer:
v = 9.936 m/s
Explanation:
given,
height of cliff = 40 m
speed of sound = 343 m/s
assuming that time to reach the sound to the player = 3 s
now,
time taken to fall of ball


t = 2.857 s
distance
d = v x t
d = v x 2.875
time traveled by the sound before reaching the player



distance traveled by the wave in this time'
r = 0.143 x 343
r= 49.05 m
now,
we know.
d² + h² = r²
d² + 40² = 49.05²
d =28.387 m
v x 2.875=28.387 m
v = 9.936 m/s
His knees are flat in front of him or 180 degrees, i hope that answered your question