A light ray just grazes the surface of the Earth (M = 6.0 × 10 24 kg, R = 6.4×10 6 m). Through what angle α is the light ray bent by gravitational lensing? (Ignore the refractive effects of the Earth’s atmosphere.) Repeat your calculation for a white dwarf (M = 2.0 × 10 30 kg, R = 1.5 × 10 7 m) and for a neutron star (M = 3

Respuesta :

Answer:

(a). The deflection angle is [tex]2.77\times10^{-9}\ rad[/tex]

(b). The deflection angle is  [tex]3.95\times10^{-4}\ rad[/tex]

(c). The deflection angle is [tex]7.41\times10^{-1}\ rad[/tex]

Explanation:

Given that,

Mass of earth [tex]M_{e}=6.0\times10^{24}\ kg[/tex]

Radius of earth [tex]R_{e}=6.4\times10^{6}\ m[/tex]

Mass of white dwarf [tex]M=2.0\times10^{30}\ kg[/tex]

Radius of white dwarf [tex]R=1.5\times10^{7}\ m[/tex]

Mass of Neutron [tex]M=3.0\times10^{30}\ kg[/tex]

Radius of neutron [tex]R=1.2\times10^{4}\ m[/tex]

We need to calculate the deflection angle for earth

Using formula of angle

[tex]\alpha=\dfrac{4G M}{c^2R}[/tex]

Where, R = radius

G = gravitational constant

M = mass

c = speed of light

Put the value into the formula

[tex]\alpha=\dfrac{4\times6.67\times10^{-11}\times6.0\times10^{24}}{(3\times10^{8})^2\times6.4\times10^{6}}[/tex]

[tex]\alpha=2.77\times10^{-9}\ rad[/tex]

The deflection angle is [tex]2.77\times10^{-9}\ rad[/tex]

We need to calculate the deflection angle for white dwarf

Using formula of angle

[tex]\alpha=\dfrac{4G M}{c^2R}[/tex]

Put the value into the formula

[tex]\alpha=\dfrac{4\times6.67\times10^{-11}\times2.0\times10^{30}}{(3\times10^{8})^2\times1.5\times10^{7}}[/tex]

[tex]\alpha=3.95\times10^{-4}\ rad[/tex]

The deflection angle is [tex]3.95\times10^{-4}\ rad[/tex]

We need to calculate the deflection angle for neutron star

Using formula of angle

[tex]\alpha=\dfrac{4G M}{c^2R}[/tex]

Put the value into the formula

[tex]\alpha=\dfrac{4\times6.67\times10^{-11}\times3.0\times10^{30}}{(3\times10^{8})^2\times1.2\times10^{4}}[/tex]

[tex]\alpha=7.41\times10^{-1}\ rad[/tex]

The deflection angle is [tex]7.41\times10^{-1}\ rad[/tex]

Hence, This is the required solution.