Question

Which kind of telescope uses mirrors to collect light? A) radio B) electromagnetic C) refracting D) reflecting

Short answer

D) reflecting

Step-by-step solution

Understand the Options

We have four options: radio, electromagnetic, refracting, and reflecting. Let’s first consider what each type of telescope does.

Identify Telescope Types

A radio telescope is designed to detect radio waves from space. An electromagnetic telescope is not a specific type; it's a broad term that could encompass any telescope that detects any form of electromagnetic radiation. A refracting telescope uses lenses, while a reflecting telescope uses mirrors.

Match Telescope Type to Feature

Since the question specifically asks about a telescope that uses mirrors to collect light, we need to determine which telescope fits this feature. Given our options, a refracting telescope uses lenses, leaving the reflecting telescope, which is indeed the type that uses mirrors.

Select the Correct Answer

Based on the matching of the telescope types to their methods of collecting light, the reflecting telescope uses mirrors.

Key concepts

Reflecting Telescope

A reflecting telescope is a type of telescope that uses mirrors to gather and focus light. It was invented by Sir Isaac Newton in the 17th century and has since become one of the most popular types of telescopes for both amateur and professional astronomers.
Reflecting telescopes use a primary mirror to collect light from the night sky. This mirror is usually parabolic in shape to minimize aberrations and to focus the light onto a secondary mirror or directly into an eyepiece. The primary mirror surface reflects the light to a focal point, which is then analyzed or viewed.
Benefits of reflecting telescopes include their ability to capture large amounts of light, making them ideal for viewing faint and distant objects in the universe.

• They don't suffer from chromatic aberration, a problem that affects refracting telescopes due to the dispersion of light through lenses.
• The use of mirrors instead of lenses allows reflecting telescopes to be constructed at larger apertures than refracting types.
• They're typically more cost-effective to build for large-sized telescopes.

Refracting Telescope

Refracting telescopes, also known as refractors, are the oldest type of telescope and were first used by Galileo in 1609. They use lenses to bend light and bring it to a focus. The main lens, called the objective lens, gathers light and bends it into a focal point to create an image.
The design of a refracting telescope typically involves two key lenses: the objective lens and the eyepiece lens. The objective lens is located at the front end of the telescope and is responsible for collecting and focusing incoming light. The eyepiece lens then magnifies the image formed by the objective lens, allowing the observer to see the details.
Benefits of refracting telescopes include:

• Low maintenance: Unlike reflecting telescopes, there are no mirrors to adjust.
• Sharp, crisp images, free from the diffraction spikes that can affect reflectors.
• Closed tube design, which helps keep out dust and debris.

However, refractors can suffer from chromatic aberration—a misalignment of colors caused by the lens's dispersion of light. Advanced designs have reduced this effect, but it's still a consideration compared to reflectors.

Radio Telescope

Radio telescopes are used to study celestial objects that emit radio waves, which are a type of electromagnetic radiation. Unlike optical telescopes which observe the universe in visible light, radio telescopes can observe through clouds, dust, and the Earth's atmosphere, allowing observations of phenomena that are otherwise obscured.
These telescopes consist of large parabolic antennas or dishes to capture radio waves. The dish acts like a gigantic mirror, reflecting radio waves to a focal point where they are received and processed.

• The size of the dish determines the resolving power of the radio telescope—a larger dish provides more detail in the observation.
• Radio telescopes can be wired together in arrays, providing an even higher resolution by synthesizing a much larger effective telescope.
• Important in detecting cosmic microwave background radiation, studying space objects like pulsars, and discovering distant galaxies.

Their ability to "see" invisible radio waves extends our understanding of the universe beyond what is possible with only visual observations.

Mirror Use in Telescopes

Mirrors play a crucial role in telescopes by allowing devices to capture and focus light efficiently. In reflecting telescopes, mirrors are the primary component used to direct light into a viewable image.
The primary mirror in a reflecting telescope gathers light and reflects it to a single point known as the focal point. This mirror is typically parabola-shaped to minimize spherical aberration and improve image quality.
A secondary mirror is often used to redirect the focused light into an eyepiece or detector, depending on the telescope's design.

• Mirrors in telescopes can be lighter and more cost-effective than large lenses, leading to larger telescopes with higher light-gathering ability.
• They can be precisely shaped, allowing for correcting optical errors that a single lens may encounter.
• Not affected by chromatic aberration, as mirrors reflect all wavelengths of light equally.

The role of mirrors revolutionized the design and functionality of telescopes, making them powerful tools for deep-space exploration.