Law of Reflection
The law of reflection Consider a light-ray incident on a plane mirror, the angle of reflection is equal to the incidence angle. This is the law of reflection. When looking at the end of the head … more
Maximum Elongation of Inner Planets
Maximum Elongation of Inner Planets From the Earth’s perspective, the inner planets seem to stay near the sun. This is because it orbits the inside of the earth. So We cannot see the inner planets in … more
Fourier Analysis
Fourier series A Fourier series is a way to represent a function as the sum of simple sine waves. A simple trigonometric function consists of a smooth surface. If you continue to add these trigonometric functions, … more
Formation Model of Columnar Joint
Formation of Columnar Joint A columnar joint appears as a polyhedral pillar, such as a tetragonal, pentagonal, or hexagonal shape. Its shape depends on the rate at which the lava solidifies. Columnar joints are often mistakenly … more
Differentiation
Differentiation The differentiation is to find the amount of change at a point on a graph f(x). This is like the process of finding the slope of the tangent line when you can draw a tangent … more
Stellar Parallax
Parallax When an object is close to me, you can use a ruler to measure the distance. But, it isn’t easy to measure when the object is away from me. In this case, how can you … more
Horizontal Coordinate System
Celestial coordinate system A celestial sphere is an abstract sphere centered on an observer. All objects in the sky can be conceived as projected upon the celestial sphere’s inner surface. Horizontal Coordinate System The horizontal Coordinate … more
Equatorial Coordinate System
Celestial coordinate system A celestial sphere is an abstract sphere centered on an observer. All objects in the sky can be conceived as projected upon the celestial sphere’s inner surface. Equatorial system The equatorial coordinate system … more
Constellations
Constellations If you look at the sky where there is no light on a clear night, there are so many stars that can not count. Thousands of years ago, the ancients linked stars to create constellations … more
Chemical Change of Candle
Paraffin, the main ingredient of candles Paraffin, the main ingredient of candles, is alkane hydrocarbons in which 20 to 40 carbon atoms are linked in a chain. It does not dissolve in water as a polar … more
Celestial Equator and the Ecliptic
The tilt relationship of the celestial sphere and ecliptic The celestial equator is the enlargement of the earth’s equator to the celestial sphere. Therefore, the celestial equator can be represented by a line fixed on the … more