● The kilogram was redefined for the first time in 130 years in May 2019 and it will now be redefined by a fundamental property of nature known as Planck’s Constant.

● It is denoted by a physical constant that is the quantum of electromagnetic action which relates the energy carried by a photon to its frequency.

• The lens-type commonly used for correcting presbyopia is Bifocal Lens.

• An eye that suffers from myopia as well as from hypermetropia is said to suffer from Presbyopia.

• Presbyopia is the normal loss of near focusing ability that occurs with age and people begin to notice the effects of presbyopia sometime after age 40.

Speed of sound = Wavelength x Frequency

250 m/s = 2m x Frequency

Frequency = 125 s^-1

Time period = 1/Frequency

Time period = 1/125 = 0.008s

* LIDAR stands for Light Detection and Ranging. It is also called 3D laser scanning.

* It is commonly used to make high-resolution maps.

Since 1 watt = 1 joule/second

As 20 watt heating filament kept on for 2 seconds ;

→ Heat released by filament = 20 × 2 = 40 Joule

• If the Distance-Time graph is a curve then it represents non-uniform speed.

• Distance-time graph is a plot that represents the distance covered in the given time interval. In other words, it tells us about the speed of the vehicle while travelling a certain distance.

Buoyant forces help swimmers to float in water.

* The buoyant force acts through the center of buoyancy, which is the centroid of the immersed part of the object; this is the volume of water that is displaced by the object.

* Note that for balancing the body while swimming, the buoyancy force must pass through the center of mass.

* There are major four forces that apply to swimmers. They are- Buoyant Force, Weight, Drag Force and Thrust Force.

a) Kelvin is the SI unit of the temperature and it is represented by ‘K’.

b) 0 kelvin = -273.15 degree celsius.

c) The degree or intensity of heat present in a substance or object, especially as expressed according to a comparative scale is called temperature.

a) 20Hz- 20000Hz is the audible range of sound for an average adult human being.

b) Human infants can actually hear frequencies slightly higher than 20 kHz.

c) The SI unit of audio frequency is the hertz (Hz).