The power of the lens is 2 diopter means that this lens has a focal length of 1/2 meter.
The focal length = 1 ÷ ( the number of diopters)
If one's glass prescription shows that the power of the lens is 2 diopter it means that the person is far-sighted. It means if a person needs to see something which is quite distant then his eyes need extra lens power to focus on it. Moreover, if there's a sign convention it means '+' indicates a convex lens and '-' concave lens. Also in-camera close up lens are also measured in terms of diopter.
I hope this answer helps.
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Answer:
The value is 
Explanation:
Generally from the calorimetry principle we have that
So here heat gained water is mathematically represented as i.e
substituting 0.150 kg for 
, 4200 J/kg.°C for 
, 100°C for 
and 75°C for T
We have
The Heat loss by the ice is mathematically represented as
Here 
is the energy to move the ice to its melting point which is evaluated as
Here 
is the mass of ice
is the specific heat of ice with value 
temperature of ice at melting point with value 0°C
is the temperature of ice with value -12°C
is the energy to move the ice from its its melting point to liquid which is evaluated as
Here L is the Latent heat of melting of ice with value 
is the energy to move the ice from liquid to the equilibrium temperature which is evaluated as
So
![Q_i = m_i [ c_i * ( T_o -T_i) + L + c_w * ( T -T_o) ]](https://tex.z-dn.net/?f=Q_i%20%20%3D%20m_i%20%5B%20c_i%20%2A%20%28%20T_o%20-T_i%29%20%2B%20L%20%20%2B%20c_w%20%2A%20%28%20T%20-T_o%29%20%5D%20)
=> ![Q_i = m_i [ 2.05 * 10^3 * ( 0 -(-12)) + 334 * 10^3 + 4200 * ( 75 - 0) ]](https://tex.z-dn.net/?f=Q_i%20%20%3D%20m_i%20%5B%202.05%20%2A%2010%5E3%20%2A%20%28%200%20-%28-12%29%29%20%2B%20334%20%2A%2010%5E3%20%20%2B%20%204200%20%2A%20%28%2075%20-%200%29%20%5D%20)
From
We have that
=> 
=>
Answer:
14J
20000J
200J
Explanation:
formula :W=FS
W:work done
F:force (N)
S:displacement moved in direction of force (m)
1) 20N×0.7m
=14J
2) 400N×50m
= 20000J
3) 10N×20m
=200J
