Banu's blog for school students

The outer covering of a cell is called plasma membrane. It is made of lipids and proteins. It defines the shape and size of a cell, encloses cytoplasm and protect it from external environment.  Any substance enters or leaves the cell through this membrane only. This exchange of substances through this membrane occurs very selectively hence it is known as 'selectively permeable membrane'.   Experiment to observe plasma membrane.  Take a rheo leaf ,tear it in single stroke  and observe it against the light. Take a small piece of light colored transparent portion keep it on a slide, put one drop of water and observe it under a microscope.  Now put some dilute salt solution over the specimen and observe it under a microscope.  The salt solution removes the water present inside the cell and hence resulting in shrinking of cytoplasm. The outer boundary of cytoplasm is plasma membrane.  The separated layer is called the cell wall. It is made up of cellulose. I

What Is Light Energy? The sun emits an enormous amount of electromagnetic radiation (solar energy). Humans can see only a fraction of this energy, which is referred to as “visible light.” The manner in which solar energy travels can be described and measured as waves. Scientists can determine the amount of energy of a wave by measuring its wavelength, the distance between two consecutive, similar points in a series of waves, such as from crest to crest or trough to trough .  Do you listen to radio ,or watch television Or use microwave oven?? All these devices make use of electromagnetic waves. Radio waves, micro waves,X rays, visible light are all examples of electromagnetic waves which differ from each other in wavelength. Electromagnetic waves are produced by the motion of electrically charged particles. These waves are also called as "electromagnetic radiation" because they radiate from electrically charged particles. They travel through space as well as through air and ot