The answer would be B, George Darwin :)
Answer:

Explanation:
By Einstein's Equation of photoelectric effect we know that

here we know that
= energy of the photons incident on the metal
= minimum energy required to remove photons from metal
= kinetic energy of the electrons ejected out of the plate
now we know that it requires 351 nm wavelength of photons to just eject out the electrons
so we can say

here we know that

now we have

now by energy equation above when photon of 303 nm incident on the surface





Soory i think multiple of velocity and angle
Answer
mass of the block A = 20 Kg
mass of block B = 10 Kg
acceleration of Block A = ?
acceleration of Block B = ?
Assuming the magnitude of force = 124 N
Applying newton's second law
F = 2 T
T = F/2
now, Tension in the string =
T = 124/2 = 62 N
Weight of the block A
W = m₁ g
W = 20 x 9.8 = 196 N
Weight of the block B
W = m₂ g
W = 10 x 9.8
W = 98 N
Weight of blocks is greater than force applied by the pulley so, the blocks will not move.
Hence, acceleration of the block A and B = 0 m/s²
If the Force magnitude is increased to 294 N
T = F/2 = 294/2 = 147 N
Since this Force is less than Weight A acceleration of the block A = 0 m/s².
For Block B
Tension is more than Weight hence block will move
Net Force = 147 - 98 = 49 N
acceleration =

a = 4.9 m/s²
Caves are formed by the dissolution of limestone. Rainwater picks up carbon dioxide from the air and as it percolates through the soil, which turns into a weak acid. This slowly dissolves out the limestone along the joints, bedding planes and fractures, some of which become enlarged enough to form caves