Yes that is correct or in other form, True
Answer:
Minimum number of photons required is 1.35 x 10⁵
Explanation:
Given:
Wavelength of the light, λ = 850 nm = 850 x 10⁻⁹ m
Energy of one photon is given by the relation :
....(1)
Here h is Planck's constant and c is speed of light.
Let N be the minimum number of photons needed for triggering receptor.
Minimum energy required for triggering receptor, E₁ = 3.15 x 10⁻¹⁴ J
According to the problem, energy of N number of photons is equal to the energy required for triggering, that is,
E₁ = N x E
Put equation (1) in the above equation.

Substitute 3.15 x 10⁻¹⁴ J for E₁, 850 x 10⁻⁹ m for λ, 6.6 x 10⁻³⁴ J s for h and 3 x 10⁸ m/s for c in the above equation.

N = 1.35 x 10⁵
(a) The plastic rod has a length of L=1.3m. If we divide by 8, we get the length of each piece:

(b) The center of the rod is located at x=0. This means we have 4 pieces of the rod on the negative side of x-axis, and 4 pieces on the positive side. So, starting from x=0 and going towards positive direction, we have: piece 5, piece 6, piece 7 and piece 8. Each piece is 0.1625 m long. Therefore, the center of piece 5 is at 0.1625m/2=0.0812 m. And the center of piece 6 will be shifted by 0.1625m with respect to this:

(c) The total charge is

. To get the charge on each piece, we should divide this value by 8, the number of pieces:

(d) We have to calculate the electric field at x=0.7 generated by piece 6. The charge on piece 6 is the value calculated at point (c):

If we approximate piece 6 as a single charge, the electric field is given by

where

and d is the distance between the charge (center of piece 6, located at 0.2437m) and point a (located at x=0.7m). Therefore we have

poiting towards the center of piece 6, since the charge is negative.
(e) missing details on this question.
Answer:0.25 times
Explanation:
Given
Distance of satellite from earth surface=Radius of earth
Force on the satellite is F=mg'
where g'=acceleration due to gravity at that point
Distance from center of Earth=R+R=2R
Gravitational Force is given by

Force 
Force on earth surface 
Divide 1 and 2 we get

He proposed the sun-centered model of the solar system.