ch 4 Light and Telescopes Lecture Review

Flashcards covering key vocabulary related to light and telescopes from the lecture 'Understanding Our Universe, 4th Edition, Chapter 4'.

Speed of Light

Light moves at 300,000 km/s in space, first measured by Rømer by observing Jupiter’s moons.

Electromagnetic Wave

Light is a type of wave that does not require a material (medium) through which to travel, unlike sound or water waves.

Wavelength (λ)

The length between two consecutive crests of a wave.

Amplitude

The height of a wave from its undisturbed position.

Speed (v) of a wave

How fast a wave travels.

Frequency (f)

The number of waves that pass by a point each second. Related to wavelength and speed by the formula c = λf.

Spectrum

Light sorted by its frequency and wavelength.

Visible Spectrum

The small part of the full electromagnetic spectrum that human eyes can see, ranging from red (longest wavelength) to violet (shortest wavelength).

Spectrographs (Spectrometers)

Instruments that break up light into different wavelengths.

Photon

A particle of light that carries energy. Its energy is directly proportional to its frequency.

Unique Spectra

Each element and molecule interacts with light in a distinctive way, creating a unique pattern of absorbed or emitted wavelengths, which allows astronomers to determine composition, temperature, and density.

Atom

Consists of a dense nucleus (protons and neutrons) surrounded by negatively charged electrons.

Molecules

Consist of two or more atoms bound by chemical bonds.

Absorption

The process by which light energy is taken in by matter.

Emission

The process by which matter releases energy, often in the form of light.

Digital Detectors

Devices like charge-coupled devices (CCDs) that are more efficient than film for recording astronomical data. They contain an array of pixels that create electric charges when struck by photons, forming an image.

Refraction

The bending of light as it enters or leaves a material because its speed is different in different media, fundamental to how a lens works.

Reflection

The bouncing of light off a surface, such as a mirror.

Refracting Telescopes

Telescopes that use lenses to collect and focus light.

Focal Length

The distance from a lens or mirror to where the light focuses. A longer focal length produces a larger image.

Aperture

The diameter of the primary lens or mirror in a telescope. A larger aperture collects more light.

Reflecting Telescopes

Telescopes that use mirrors to collect and focus light.

Earth's Atmosphere (effects on light)

Blocks nearly all gamma ray, X-ray, ultraviolet, and infrared wavelengths, but is transparent to visible light and a large range of radio waves.

Radio Telescopes

Large telescopes, typically tens of meters in diameter, designed to collect radio waves which have long wavelengths (1 cm to 10 m).

Interferometric Arrays

Systems that combine signals from multiple telescopes to act as one large telescope, improving angular resolution.

Space-Based Telescopes

Telescopes placed in space (e.g., Hubble, Chandra) to avoid the distorting and blocking effects of Earth's atmosphere.

Diffraction

The spreading out of light waves when passing through an aperture, which blurs the image.

Angular Resolution

The smallest detail that can be distinguished or separated in an image. Larger aperture generally leads to better resolution.

Astronomical Seeing

The limit on resolution caused by atmospheric distortion.

Adaptive Optics

Technology used to correct for atmospheric distortion in ground-based telescopes, allowing them to achieve image quality comparable to space telescopes.