Biomedical Engineering Reference
In-Depth Information
he.diference.in.the.travel.time.can.then.be.written.as
−
h
s
h
s
n
−
h
R
1
2
2
1
2
t
−
t
=
+
OPI
OI
c
c
2
2
.
1
2
For.the.travel.times.along.the.two.routes.to.be.equal,.we.need
=
h
s
h
s
n
−
h
R
1
2
2
1
2
+
c
c
2
2
1
2
=
1
2
1
2
)
1
(2.5)
(
+
n
−
1
s
s
R
1
2
)
1
1
2
(
+
=
n
−
1
s
s
R
.
.
1
2
In.the.limit.that.
s
1
.→ ∞,.we.have
1
)
2
(
=
n
−
1
s
R
2
R
1
=
s
=
f
2
n
−
1 2
.
In.the.limit.that.
s
2
.→ ∞,.we.have
R
1
=
s
=
f
1
n
−
1 2
.
herefore,.the.focal.lengths.would.be.the.same.on.either.side.of.the.lens,.and.the.light.that.comes.in.
from.ininity.is.brought.to.a.focus.at.a.distance.
f
.from.the.lens..If.the.radii.of.curvature.
R
1
.and.
R
2
.on.
either.side.of.the.lens.are.not.equal,.and.using.the.convention.that.the.radius.of.curvature.is.positive.if.
the.center.of.the.radius.of.curvature.is.to.the.right.of.the.lens.(
R
1
).and.is.negative.if.the.center.is.to.the.
let.of.the.lens.(
R
2
),.then.we.would.have
h
R
2
h
R
2
VQ
=
QV
'
= −
2
2
.
1
2
and
1
1
1
1
(
)
+
=
n
−
−
1
s
s
R
R
.
1
2
1
2
In.the.limit.that.
s
1.
→ ∞,.we.have
1
1
1
(
)
=
n
−
1
−
s
R
R
2
1
2
=
f
.
1
R R
R
s
=
1
2
2
n
−
1
−
R
.
2
1
