NBSE class 10 syllabus

1. HUMAN EYE AND THE COLOURFUL EYE
• HUMAN EYE:
• Functions of iris
and pupil is to regulate
Amount of light entering
The eye
Working of eye:
Light enters> focused on the retina by eye lens> forms
real and inverted image> takes the signals to brain by
optic nerve> brain interprets the image

2. Power of accomodation of eye
• The ability of the eye lens to adjust its focal
length with the help of ciliary muscles so as to
see nearby as well as distant objects clearly.
Far point: the maximum distance upto which the
eye can see i.e infinity for normal eye
Near point: the minimum distance upto which
the eye can see i.e 25 cm for normal eye
Least distance of distinct vision=25 cm

3. DEFECTS OF VISION
• HOW IT OCCURS?
Weakening of ciliary muscles,change in the size
of eye ball,irregularities on the surface of
cornea,formation of hazy membrane over the
eye-lens etc.

4. MYOPIA(SHORT SIGHTEDNESS)
• It is a defect of vision in which a human eye can see
nearby objects clearly or distinctly but far off objects
appear blurred.
• CAUSES:
>High converging power of eye lens(contraction of
eye lens)
>Elongation of eye ball(distance between lens and
retina increases)
CORRECTION:
Can be corrected by using Concave lens of suitable focal
length.

5. Ray diagram

6. HYPER METROPIA(FAR SIGHTEDNESS)
• It is a defect of eye in which the person can see distant
objects clearly but nearby objects appear blurred.
• CAUSES:
>Low converging power of eye lens(relaxation of ciliary
muscles)
>Contraction of eye ball(distance between the eye lens
and retina decreases)
CORRECTION:
Can be corrected by using convex lens of suitable focal
length.

7. Ray diagram

8. OTHER DEFECTS OF EYE
• PRESBYOPIA:
In this defect a person cannot see nearby and far off
objects clearly.
Causes:
>Gradual weakening of ciliary muscles
Correction: Bifocal lens
• ASTIGMATISM;
It is a defect in the outer curvature of the eye.
Causes: cornea for not being spherical
Correction: cylindrical lens.

9. REFRACTION OF LIGHT THROUGH A
PRISM
• In prism the light gets refracted in towards the
base of prism.

10. DISPERSION OF WHITE LIGHT BY A
PRISM
• The phenomenon of splitting up of white light
into its constituent colours on passing through
a prism is called dispersion
• The band of 7 colors obtained on the screen is
called spectrum.
• It is caused due to different speed of
wavelength in different medium.
• Red light is least deviated and violet is most
deviated.

11. DISPERSION OF WHITE LIGHT BY A
PRISM

12. RECOMBINATION OF THE SPECTRUM
OF WHITE LIGHT

13. ATMOSPHERIC REFRACTION
• TWINKLING OF STARS
The light from stars reaches us after
atmospheric refraction . The atmosphere
Is not steady because of the change in
Temperature and air mobility. Therefore,
The refractive index of air in given region
keeps on changing continuously and
Randomly. Due to this the amount of
Light reaching us is not always the same
Therefore the stars appear twinkling.

14. ATMOSPHERIC REFRACTION
• ADVANCE SUNRISE AND DELAYED SUNSET
The Sun is visible to us about 2 minutes
before the actual sunrise, and about 2
minutes after the actual sunset because
of atmospheric refraction. By actual
sunrise, we mean the actual crossing of
the horizon by the Sun. Fig. shows the
actual and apparent positions of the
Sun with respect to the horizon. The
time difference between actual
sunset and the apparent sunset is about 2
minutes. The apparent flattening of the Sun’s disc at sunrise and sunset is also
due to the same phenomenon.

15. SCATTERING OF LIGHT
• TYNDALL EFFECT
• WHY IS THE COLOUR OF THE CLEAR SKY BLUE
• COLOUR OF SUN AT SUNRISE AND SUNSET