18. Calculations

Question 1

Position of an image for a spherical mirror

Answer 1

1/v - 1/u = 1/f = 2/4

v - distance image from mirror
u - distance object from mirror
f - focal length
r - radius

Question 2

Magnificaiton

Answer 2

ratio of I to O

I / O = - v / u

I - image size
O - object
v - distance image from mirror
u - distance object from mirror

Question 3

Surface power

Answer 3

Snell’s law sin i / sin r

(n2-n1) / r

r - radius in metres
n2 - new medium
n1 - old medium

Question 4

Refracting angle of a prism

Answer 4

1 dioptre = 1/2 angle

Question 5

Angle of deviation

Answer 5

(n-1) x refracting angle

Question 6

Thin lens formula

Answer 6

1 / V - 1/U = 1/f2

V - distance of image from principal point
U - object
f2 - second focal length in metres

Question 7

Vergence power

Answer 7

F - 1/ f2

f2 in metres

Question 8

Linear magnification

Answer 8

I / O = v / u

Question 9

magnification of a magnifiyer

Answer 9

M = F / 4

Question 10

Prismatic effect

Answer 10

P = F X D

D is cms

Question 11

Conversion to CL

Answer 11

Fcl = Fgl - vertex distance

all in mm

then CL power 1 / Fcl

Question 12

Spherical equlivant

Answer 12

SE = DS + 1/2 DC

Question 13

Amplitude of accomodation

Answer 13

A = P - R

P - near in dioptres
R - far in dioptres

Question 14

Power of correcting lens moveed

Answer 14

Fn = Fo / (1 - dFo)

Fo = power in orgingal
Fn = power in new
dFo = distance moved in metres

Question 15

Magnification of galilean systemt

Answer 15

M = Fe / Fo

Fe - eye piece
Fo - objectiveL

Question 16

Linear magnification in indirect ophthalmoscopy

Answer 16

Liner mag = FL of lens / distance

Focal length of condensening lens / distance between ndoal point and the retina