Advantages of cassegrain telescope is/are

Options

A. Free of chromatic aberration
B. High resolving power
C. Free of spherical aberration
D. All of these

Answer

### Step-by-Step Solution:

1. **Understanding the Cassegrain Telescope**:
- The Cassegrain telescope is a type of reflecting telescope that uses a combination of mirrors to focus light. It typically consists of a large concave mirror (the primary mirror) and a smaller convex mirror (the secondary mirror).

2. **Chromatic Aberration**:
- One of the main advantages of the Cassegrain telescope is that it is free from chromatic aberration. Chromatic aberration occurs in lenses when different wavelengths of light are focused at different points, leading to color fringing in images. Since mirrors do not refract light, the focal length of a mirror is independent of the wavelength of light, thus eliminating this issue.

3. **High Resolving Power**:
- The Cassegrain telescope also has a high resolving power compared to lens telescopes. Resolving power refers to the ability of a telescope to distinguish between two closely spaced objects. Mirrors can be made larger than lenses, allowing for better resolution.

4. **Free of Spherical Aberration**:
- Another advantage is that Cassegrain telescopes are free from spherical aberration. Spherical aberration occurs in lenses when light rays that strike the lens near its edge focus at different points than those that strike near the center. In mirrors, particularly parabolic mirrors, this issue is minimized, leading to clearer images.

5. **Conclusion**:
- Therefore, the advantages of the Cassegrain telescope include:
- It is chromatic aberration free.
- It has high resolving power.
- It is free of spherical aberration.
- Thus, all the mentioned advantages are correct, making the answer option four: "All of these."