It is D because our eye lenses reflect the white light we see and it also reflects the light to a point to where we can see colors and objects clearly... Hope this helps out ^-^''
Answer:
Pressure,P=6×10^3Pa
Explanation:
The gas has an ideal gas behaviour and ideal gas equation
PV=NKT
T= V/N p/K ...eq1
Average transitional kinetic energy Ktr=1.8×10-23J
Ktr=3/2KT
T=2/3Ktr/K....eq2
Equating eq1 and 2
V/N p/K = 2/3Ktr/K
Cancelling K on both sides
P= 2/3N/V( Ktr)
Substituting the value of N/V and dividing by 10^-6 to convert cm^3 to m^3
P = 2/3 (5.0×10^20)/10^-6 × 1.8×10^-23
P= 6 ×10^3Pa
Similarities:
The halogens like noble gases are gaseous im nature. Example,
Chlorine, bromine are halogens and argon , xenon are noble gases.
Both are non-metals.
Differences: Halogens are very reactive because their octet needs only one electron tk complete. But, the nobles gases are quite stable and unreactive because the have complete octets.
Answer:

T=157.06 N
Explanation:
Given that
Mass of first block = 21.1 kg
Mass of second block = 12.9 kg
First mass is heavier than first that is why mass second first will go downward and mass second will go upward.
Given that pulley and string is mass less that is why both mass will have same acceleration.So lets take their acceleration is 'a'.
So now from force equation

21.1 x 9.81 - 12.9 x 9.81 =(21.1+12.9) a

Lets tension in string is T


T=21.1(9.81-2.36) N
T=157.06 N