Physics Chapter: Electromagnetic Spectrum & Atomic Structure

A wave is a disturbance that travels through a medium or space in a regular and organized pattern.

Transverse waves have oscillations perpendicular to the direction of wave propagation. Imagine a rope tied to a post and you move the rope up and down. The wave travels horizontally, but the rope oscillates vertically.

Longitudinal waves have oscillations parallel to the direction of wave propagation. Imagine a slinky being compressed and expanded. The compression and expansion travel along the slinky.

Light is a self-propagating, transverse electromagnetic wave that can travel through a vacuum. This means it has both magnetic and electric components oscillating perpendicular to each other.

The wavelength (λ) of a wave is the distance between two consecutive peaks or troughs. It's usually measured in nanometers (nm) or meters (m).

The frequency (ν) of a wave is the number of peaks that pass a fixed point per second. It's measured in Hertz (Hz), which is equivalent to cycles per second or s^-1.

The speed of a wave is related to its wavelength and frequency. It's calculated as the product of wavelength and frequency. The speed of light in a vacuum is a constant, approximately 3 x 10^8 meters per second.

Light can also be described as a stream of particles called photons. Each photon carries energy related to its wavelength and frequency.

Energy levels are quantized - electrons can only exist at specific energy levels, like steps on a staircase. They cannot exist between these levels.

An electron absorbs a photon and jumps to a higher energy level. When it falls back down, it emits a photon.

The energy of the absorbed or emitted photon corresponds to the energy difference between the two energy levels involved in the transition.

The specific wavelengths of light emitted or absorbed by an atom create a unique spectral fingerprint, like a barcode identifying the element.

A spectrum with all wavelengths visible, like from an incandescent light bulb.

A spectrum with bright lines at specific wavelengths, produced by excited atoms emitting light.

A spectrum where absorption lines (dark lines) appear at specific wavelengths, as atoms in a cooler gas absorb photons.

The process of removing an electron from an atom, creating a positively charged ion.

The complete spectrum of all forms of light, including visible light, radio waves, microwaves, infrared, ultraviolet, X-rays, and gamma rays.

A form of light that is not visible to the human eye.

A measure of the distance between two consecutive peaks or troughs of a wave.

A measure of the number of peaks passing a fixed point each second.

The smallest unit of matter, consisting of neutrons, protons, and electrons.

Atoms that have gained or lost electrons, giving them a net electric charge.

Versions of the same element with different numbers of neutrons in their nucleus.

Specific energy levels that electrons can occupy within an atom, where energies between these levels are not allowed.

The smallest detail a telescope can distinguish, determined by the diameter of the telescope's objective lens/mirror.

The ability of a telescope to collect light from distant objects. Larger telescopes gather more light, making fainter objects visible.

The bending of light as it passes through the Earth's atmosphere, causing stars to appear blurry.

A technique that uses rapidly adapting mirrors to counteract atmospheric blurring, resulting in sharper telescope images.

Excessive artificial lighting that makes it difficult to see faint astronomical objects.

The position of an object directly overhead in the sky.

Observing from high altitudes reduces the amount of atmosphere that light has to travel through, increasing the chance of clear images.

Placing telescopes in space avoids atmospheric interference completely, resulting in the sharpest possible images.

All large, dense objects emit light across a range of wavelengths, forming a continuous spectrum. This spectrum depends only on the object's temperature and is called a thermal spectrum.

Hotter objects emit more light at all wavelengths compared to cooler objects. Thus, a hotter object will appear brighter.

Hotter objects emit photons with a higher average energy. This means the peak of the thermal spectrum shifts toward shorter wavelengths (higher frequencies).

Wien's Law describes the relationship between the temperature of an object and the wavelength at which its thermal spectrum peaks.

Wien's Law states that the peak wavelength (λmax) is inversely proportional to the temperature (T) of the object. This means that as the temperature increases, the peak wavelength decreases.

Sirius, the brightest star in the night sky, has a peak wavelength of 290 nm. Using Wien's Law, we can calculate its surface temperature.

Humans emit infrared radiation, which is invisible to our eyes. We are not hot enough to emit visible light.

The photo was likely taken in the infrared region of the electromagnetic spectrum, as humans emit mostly infrared radiation.

The ability of an atom to absorb or emit specific wavelengths of light, creating a unique "fingerprint" for each element.

A spectrum with bright lines at specific wavelengths, created by excited atoms emitting photons.

A spectrum with dark lines at specific wavelengths, caused by atoms absorbing photons at those wavelengths.

The phenomenon where light shifts towards shorter wavelengths (blue) when the source is moving towards the observer, and towards longer wavelengths (red) when the source is moving away.

A tool used to collect and focus light, allowing us to observe distant objects in space.

The process by which an electron gains energy and moves to a higher energy level within an atom.

The process by which an electron loses energy and transitions back down to a lower energy level within an atom.

The unit of light energy, a tiny packet of electromagnetic radiation.

Specific energy levels within an atom that electrons can occupy, with energy gaps between them.