Q12DQ - University Physics with Modern Physics

Question

With which color of light can the Hubble Space Telescope see finer detail in a distant astronomical object: red, blue, or ultraviolet? Explain your answer.

Step-by-Step Solution

Answer

The light that can be used to see distant astronomical objects is ultraviolet light.

Step 1: Given Data

Rayleigh’s criteria is a widely used criterion for the resolution of two point objects. It states that two objects are barely resolved in the center of one diffraction pattern that coincides with the first minimum of the other. In such a case, the angular separation is governed by the equation of Rayleigh’s resolving power criteria. 

The minimum separation between two objects which is resolvable by an optical instrument is called its limit of resolution. The limit of resolution is inversely proportional to the resolving power of an instrument.

Step 2: Light for telescope

According to the equation of Rayleigh’s resolving power criterion

 

$\mathrm{\theta }=1.22\frac{\mathrm{\lambda }}{\mathrm{D}}$ 

 

Where $\lambda$ = wavelength of the light ray, D = diameter of the aperture of the telescope, and $\theta$ = angular radius of the telescope.

From the above formula, it is clear that using shorter wavelengths we can detect bodies that make very short angles at the screen of the telescope. Thus, the UV light will give the best resolution to the Hubble space telescope due to its short wavelength compared to red or blue light. 

 

Therefore, the decreasing order of resolution is UV light > Blue light > Red light.