How is the Distance to the moon measured?

The speed of light is known very accurately and is 299792 kilometers per second. If a beam of light is aimed toward Moon and then reflected back, the distance from the Earth to the Moon can be worked out. For this a large telescope is required.

The mirror of the telescope is used as a searchlight’s reflecting panels stationed by astronauts on Moon. It takes 2 minute and 30 seconds to complete the total journey. The moon’s distance is then calculated. It is 384000 km from the earth.

Comments

How Many Type of Keys on a Keyboard?

Friends you know a keyboard is the most important part of a computer. It consists of different sets of keys that help us to enter information into the computer. Today we will discuss about keyboard and its keys types and use. A standard keyboard has 104 keys. Types of Keys in a Keyboard: Alphabet Keys Number Keys Special Keys Function Keys Navigation Keys 1. Alphabet Keys: 26 alphabet keys are present on a keyboard from A to Z. these keys are not present in the alphabetical order. These keys are used to type words, sentences or paragraphs. 2. Number Keys: These keys are used for typing numbers. These keys are present above the top row of the alphabet keys and also present on the right side of the keyboard. 3. Special Keys: Keyboard has more special keys such as Space bar Key, caps lock key, backspace key, shift key, enter key, symbol keys and tab key etc. 4. Function Keys: 12 function keys are present on a keyb...

Advantage and Disadvantage of Computer Generations

All computer generations have some advantage and disadvantage today we explain some computer generation advantages and disadvantages. First Generation Computers (1946-1959) The computers produced during the period 1946-1959 with the them technology are regarded as the first generation computer. These computers were manufactured with the vacuum tubes. These tubes were used in the arithmetic and logical operations. Advantages: They were capable of making arithmetic and logical operations. They used the electronic values in place of the key punch machines or the unit record machines. Disadvantages: They were too big in size, very slow, low level of accuracy and reliability. They consumed lot of electricity, generated a lot of heat and break down frequently. Second Generation Computers (1959-1965) The computer produced during the period 1959-65 with technology is known as second generation computers. These comp...

What is Vacuum Tube

A vacuum tube is, reasonable enough, a sealed glass tube containing a vacuum in which are present several electronic elements: the cathode, anode, grid, and filament. When the cathode and anode are heated by the filament, and a voltage is applied across them, current flows between the cathode and anode. If a grid is inserted between them, the flow can be controlled by changing the grid between a positive and negative voltage. The grid voltage can be quite small, and the plate voltages can be quite high, thus providing an amplifying capability. More importantly for computers, switching the grid voltage causes the tube to act as a switch with respect to the plates. Thus, we have an electronically controlled switch that is much faster than a relay. A type of vacuum tube also served as a popular storage mechanism, the Cathode Ray Tube (CRT). Other memory devices used during the period include mercury or glass delay lines, and magnetic core memory. Vacuum tubes, however, are la...

Knowledge Place

Search This Blog