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Source: The Hindu
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2021 will mark the 100th year of Einstein receiving the Nobel Prize in physics for “his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect”
Law of photoelectric effect
It argues that light is made of photons and when light shines on a metal, each photon’s energy is correlated to the electron’s speed on the metal’s surface. This theory redefined the composition of light, and it is held as a revolutionary theory, for which Einstein received the Nobel Prize in 1921.
Special theory of relativity
Einstein’s theory establishes that time moves slower within a moving body when measured from a point at rest (but moves normally within the moving body itself) and the length of the moving body contracts when measured from an outside point at rest.
When a moving body emits light, the length contraction and time slowdown of the moving body are just exactly what are needed to restore the speed of light to its constant value.
An example of the application of the special theory of relativity is the use of GPS on our phones
- Satellites account for time differences in their clocks due to their high speed and their positions away from earth’s gravity, and then calculate the geolocation.
General theory of relativity
- It tries to explain how does gravitational force act instantaneously between massive stars and planets that are millions of miles away
- Einstein took help of geometry of curved spaces and multi-dimensional geometry to understand the effect of gravitational force.
- As per this theory, space and time form a continuum, like a fabric, and every object in the universe distorts this fabric, like a large ball distorts a tight trampoline sheet. This distortion is gravity.
- It produces two effects.
- One, the fabric causes any other object in the vicinity to move towards the heavier object and this is why gravity causes an object to pull things towards it
- Two, it bends light in the process of attracting it which is recently captured by LIGO observatory
- This theory applies to all forms of motion, including those where gravity does not appear.
About LIGO
- LIGO is the world’s largest gravitational wave observatory.
- It operates three gravitational-wave detectors: Two are at Hanford, USA, and one is at Livingston, USA.
