Please help me with these 10 questions (5 points each) and please answer with proper explanation.
Answers
Answer:
11)it is given that,
power=+1.5D
positive symbol indicates that it is a convex lens and it is a converging lens..
we know that,
focal length,f=1/power=+1/1.5
f=+0.67m
12)The resultant net power,
p=p1+p2
p=-2D+1.5D
p=-0.5D
13) it is given that,
power=-0.25D
In lens, Negative symbol indicates that it is a concave lens and it is a diverging lens..
focal length=1/power
f=-1/0.25=-100/25=-4m
14)There are 3 lenses of powers,
resultant power,p=p1+p2+p3
p=2D-0.25D+1.75D
p=3.75D-0.25D
p=+3.5D
positive symbol indicates that it is a convex lens... And it is a converging lens....
15) it is given that,
v=-50cm
from the above mentioned position,
hi=ho
magnification,m=hi/ho=-v/u
ho/ho=-(-50)/u
u=50cm
focal length,1/f=1/u-1/v
1/f=1/50+1/50=2/50
f=25cm
power=100/25cm
power=4D
16) it is given that,
f=15cm,u=8cm
from the lens equation,
1/f=1/u-1/v
1/v=-8+15/120
v=120/7
so the lens are convex lens....
And it is a virtual image.....
magnification,m=-120/56
m=-15/7=-2.15
And the image is virtual, erect and magnified image.....
17) Given that,
f=-15cm,u=20cm
From the lens equation,
1/f=1/u-1/v
1/v=4-3/60
v=60cm
magnification,m=-v/u=-60/20=-3
It is a convex lens.....
18) Given that,
f=10cm, u=25cm
From the lens equation,
1/f=1/u-1/v
1/10=1/25-1/v
v=-16.6cm
magnification,m=-(-50/3×25)
m=+0.6cm
so it is a concave lens....
19) Given that,
f=-10cm,u=20cm
From the lens equation,
1/f=1/u-1/v
1/-10=1/20-1/v
v=20/3cm
magnification,m=-1/3cm
m=-0.3cm
it is a convex lens...
20)f=10cm,u=20cm,
on solving,v=-20cm
magnification,m=+1cm
it is a concave lens....
And the image is virtual image.....
Hope it helps you frnd.........
Answer:
is this for class 10..........