Physical properties are characteristics of a substance that can be observed or measured without changing the substance's chemical composition. These properties help in identifying and describing materials. Some common physical properties include: 1. **Color**: The color of the material. 2. **Odor**: The smell associated with the substance. 3. **Density**: The mass per unit volume of a substance, typically expressed in grams per cubic centimeter (g/cm³) or kilograms per cubic meter (kg/m³).

Optical phenomena refer to the various behaviors and effects of light as it interacts with different materials and media. These phenomena can include a wide range of visual effects that result from the properties of light, such as reflection, refraction, diffraction, interference, polarization, and scattering. Here are some common optical phenomena: 1. **Reflection**: The bouncing back of light when it strikes a reflective surface, such as a mirror or calm water.

Ionization refers to the process in which atoms or molecules gain or lose electrons, resulting in the formation of charged particles known as ions. This can occur through various mechanisms, including: 1. **Loss of Electrons (Cation Formation)**: When an atom or molecule loses one or more electrons, it becomes positively charged, forming a cation. This often occurs in chemical reactions, where an atom donates an electron to another atom.

Electrical phenomena refer to various effects and behaviors associated with electricity, which includes electric charge, electric fields, currents, and voltage. These phenomena can manifest in several ways and can be observed in various contexts, from simple static electricity to complex electrical circuits and electromagnetic waves. Here are some key components and concepts associated with electrical phenomena: 1. **Electric Charge**: This is a fundamental property of matter that causes it to experience a force when placed in an electromagnetic field.

Earth phenomena refer to natural processes and events that occur on Earth and are often characterized by their impact on the environment, weather, geology, and ecosystems. These phenomena can encompass a wide range of occurrences, including but not limited to: 1. **Weather Events**: Hurricanes, tornadoes, thunderstorms, heatwaves, and blizzards are examples of atmospheric phenomena that can have significant effects on the climate and human activities.

The Doppler effect is a phenomenon that occurs when there is a change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. This effect is commonly associated with sound waves, but it also applies to electromagnetic waves, such as light. ### Key Points of the Doppler Effect: 1. **Source and Observer Movement**: - If the wave source moves toward the observer, the waves are compressed, resulting in a higher frequency (or shorter wavelength).