KNOW PHYSICS

Liquids have a property that their free surface behaves like a stretched elastic membrane and has a natural tendency to contract, i.e , the free surface of a liquid tends to occupy a minimum surface area. This property of liquids is called as surface tension. Some experiments and examples related to Surface Tension- Let us consider a frame. There is a closed loop thread attached with the frame loosely, so that it can change its shape. Now dip the frame in soap solution. Break the film created inside the loop. After breaking the film, it is observed that the thread occupies a shape  of a circle. REASON - The surface tension tends to make the surface area of the film as minimum as possible. And for a given length of thread, the surface area of circle is maximum, which eventually decreases the surface area of the film to minimum. Brush in water-  When we put brush in water, the brush hair can be seen separately in water. But when we take out the brush out of the water,

  Basic Definition   PHOTOELECTRIC EFFECT| Photoelectric effect is the emission of electrons or other free carriers when electromagnetic radiation, like light, hits a material. Electrons emitted in this manner can be called photoelectrons. This phenomenon is commonly studied in electronicphysics and in fields of chemistry such as quantum chemistry and electrochemistry. A Brief History - This effect was observed earlier before Albert Einstein gave the theory for it.  In 1839, Alexandre Edmond Becquerel discovered the photovoltaic effect while studying the effect of light on electrolytic cells. Though not equivalent to photoelectric effect. The first of these phenomena was discovered by Heinrich Hertz and Wilhelm Hallwachsin 1887.  In 1887, Heinrich Hertz observed the photoelectric effect and the production and reception of electromagnetic waves. The second was first announced by Philipp Lenard in 1900. Albert Einstein's 1905 research paper ALBER