If an optical telescope focusing light of wavelength 550 nm had a perfectly ground mirror, what would have to be the minimum diameter of its mirror so that it could resolve a Jupiter-size planet around our nearest star, Alpha Centauri, which is about 4.30 light years from earth? (1 light year = 9.46×1015 m )

Respuesta :

Answer:

Diameter is 486.23 m

Solution:

Wavelength of the light, [tex]\lambda =  50\ nm[/tex]

Distance from the earth, d = [tex]4.30\ ly[/tex]

1 ly = [tex]9.46\times 10^{15}\ m[/tex]

Since, the size of the planet is that of the Jupiter, therefore,

Diameter of the planet, D = [tex]1.38\times 10^{8}\ m[/tex]

Now,

To calculate the minimum diameter:

The angular resolution is given by:

[tex]\theta = \frac{Diameter\ of\ the\ object,\ D}{Distance\ of\ the\ object,\ d}[/tex]

Distance from the earth, d = [tex]4.30\times 9.46\times 10^{15}\ m = 4.067\times 10^{16}\ m[/tex]

Now, putting the appropriate value in the above formula:

[tex]\theta = \frac{1.38\times 10^{8}}{4.067\times 10^{16}} = 3.39\times 10^{- 9}\[/tex]

Also, we know:

[tex]\theta = \frac{1.22\lambda }{D}[/tex]

[tex]\theta = \frac{1.22\times 550\times 10^{- 9}}[1.38\times 10^{- 9}} = 486.23\ m[/tex]