, Apparent size :
f ize
the an object appears to be when we look at it .
Absolute size : the true size of an object .
If an object moves away from us, its apparent size decreases, but its absolute
size stays the same.
The further awaya given object is ,
the smaller the angle subtended at the
eye .
lenses can be used to increase the fize
apparent ofa n object .
Anguar Magnification ,
M =
angle subtended by image
angle
at
-
eye
sublended by objectat
=
unaided ele
Refracting telescope raydiagram :
*For -a telescope
to work effectively ,
the focal length
of the objective
uns is much
-greater than the
Focal length of
the eyepiece .
ung
In a refracting telescope , in normal adjustment the distance between the renses
,
is equal to the sum of the focal lengths
Issues with refracting telescopes:
1) Chromatic Aberration occurs in lenses because different colours of light refract
by different amounts . This results in different colours focusing at different
points. For example , the focal length of red light is shorter than the Focal
length of blue length. This results in a
burry image ,
which limits the
detail we can .
see
, 2) magnification
Long
S
telescopes : Since M = t ogeta really large we ned
, ,
an objective uns with a
really long Focal length , fo .
This means that
powerful refracting telescopes need to be really long this makes the
refracting telescopes expensive·
3) Powerful need large since
Heavy lenses :
telescopes lenses , and the lenses
a re made up o fglass , they end up being very heavy . This means the glass
at the edges of the ens can get distoned ,
which alters the refraction
through the uns.
4) Costs : In large lenses, there a re likely to be small bubbles/ imperfections,
which a l te r light's path through the .
lens To prevent , lens manufacturers
use high qualityglass ,
which can be really .
expensive
: A minor that
concave minor reflects parallel rays to a central point .
-
Convex Minor : A mirror that diverges incident paravel rays.
f ize
the an object appears to be when we look at it .
Absolute size : the true size of an object .
If an object moves away from us, its apparent size decreases, but its absolute
size stays the same.
The further awaya given object is ,
the smaller the angle subtended at the
eye .
lenses can be used to increase the fize
apparent ofa n object .
Anguar Magnification ,
M =
angle subtended by image
angle
at
-
eye
sublended by objectat
=
unaided ele
Refracting telescope raydiagram :
*For -a telescope
to work effectively ,
the focal length
of the objective
uns is much
-greater than the
Focal length of
the eyepiece .
ung
In a refracting telescope , in normal adjustment the distance between the renses
,
is equal to the sum of the focal lengths
Issues with refracting telescopes:
1) Chromatic Aberration occurs in lenses because different colours of light refract
by different amounts . This results in different colours focusing at different
points. For example , the focal length of red light is shorter than the Focal
length of blue length. This results in a
burry image ,
which limits the
detail we can .
see
, 2) magnification
Long
S
telescopes : Since M = t ogeta really large we ned
, ,
an objective uns with a
really long Focal length , fo .
This means that
powerful refracting telescopes need to be really long this makes the
refracting telescopes expensive·
3) Powerful need large since
Heavy lenses :
telescopes lenses , and the lenses
a re made up o fglass , they end up being very heavy . This means the glass
at the edges of the ens can get distoned ,
which alters the refraction
through the uns.
4) Costs : In large lenses, there a re likely to be small bubbles/ imperfections,
which a l te r light's path through the .
lens To prevent , lens manufacturers
use high qualityglass ,
which can be really .
expensive
: A minor that
concave minor reflects parallel rays to a central point .
-
Convex Minor : A mirror that diverges incident paravel rays.
