Teacher's Diary by Rani Vaid: April 2023

OPTICS

CBSE SYLLABUS

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Reflection of light by curved surfaces.
Images formed by spherical mirrors.
Centre of curvature, principal axis, principal focus, focal length.
Mirror formula (Derivation not required).
Magnification.
Refraction
Laws of refraction
Refractive index.
Refraction of light by spherical lens
Image formed by spherical lenses
Lens formula(Derivation not required)
Magnification.
Power of a lens
Functioning of a lens in human eye
Defects of vision and their corrections
Applications of spherical mirrors and lenses.
Refraction of light through a prism
Dispersion of light
Scattering of light
Applications in daily life (excluding colour of the sun at sunrise and sunset).

CAMBRIDGE IGCSE

Light
Reflection of Light
Refraction of Light
Thin Converging Lens
Dispersion of Light
Electromagnetic Spectrum

3.1 General properties of waves continued
Core 1) Know that waves transfer energy without transferring matter 2) Describe what is meant by wave motion as illustrated by vibrations in ropes and springs, and by experiments using water waves 3) Describe the features of a wave in terms of wavefront, wavelength, frequency, crest (peak), trough, amplitude and wave speed 4) Recall and use the equation for wave speed v = f λ 5) Know that for a transverse wave, the direction of vibration is at right angles to the direction of propagation and understand that electromagnetic radiation, water waves and seismic S-waves (secondary) can be modelled as transverse 6) Know that for a longitudinal wave, the direction of vibration is parallel to the direction of propagation and understand that sound waves and seismic P-waves (primary) can be modelled as longitudinal. 7) Describe how waves can undergo: (a) reflection at a plane surface (b) refraction due to a change of speed (c) diffraction through a narrow gap 8) Describe the use of a ripple tank to show: (a) reflection at a plane surface (b) refraction due to a change in speed caused by a change in depth (c) diffraction due to a gap (d) diffraction due to an edge	Supplement 9) Describe how wavelength and gap size affects diffraction through a gap 10) Describe how wavelength affects diffraction at an edge

3.2 Light
3.2.1 Reflection Light
CORE	SUPPLEMENT
1)Define and use the terms normal, angle of incidence and angle of reflection. 2)Describe the formation of an optical image by a plane mirror, and give its characteristics, i.e. same size, same distance from mirror, virtual. 3)State that for reflection, the angle of incidence is equal to the angle of reflection; recall and use this relationship.	4) Use simple constructions, measurements and calculations for reflection by plane mirrors
3.2.2 Refraction of Light
CORE	SUPPLEMENT
1) Define and use the terms normal, angle of incidence and angle of refraction . 2) Describe an experiment to show refraction of light by transparent blocks of different shapes. 3) Describe the passage of light through a transparent material (limited to the boundaries between two media only). 4) State the meaning of critical angle 5) Describe internal reflection and total internal reflection using both experimental and everyday examples	6) Define refractive index, n, as the ratio of the speeds of a wave in two different regions . 7) Recall and use the equation n = sin i /sin r. 8) Recall and use the equation n = 1/sin c. 9) Describe the use of optical fibres, particularly in telecommunications

3.2.3 THIN LENSES
CORE	SUPPLEMENT
1) Describe the action of thin converging and thin diverging lenses on a parallel beam of light . 2) Define and use the terms focal length, principal axis and principal focus (focal point). 3) Draw and use ray diagrams for the formation of a real image by a converging lens. 4) Describe the characteristics of an image using the terms enlarged/same size/diminished, upright/inverted and real/virtual. 5) Know that a virtual image is formed when diverging rays are extrapolated backwards and does not form a visible projection on a screen.	6) Draw and use ray diagrams for the formation of a virtual image by a converging lens 7) Describe the use of a single lens as a magnifying glass 8) Describe the use of converging and diverging lenses to correct long-sightedness and short sightedness.

3.2.4 Dispersion of light
CORE	SUPPLEMENT
1) Describe the dispersion of light as illustrated by the refraction of white light by a glass prism 2)Know the traditional seven colours of the visible spectrum in order of frequency and in order of wavelength.	3) Recall that visible light of a single frequency is described as monochromatic

3.3 Electromagnetic spectrum
CORE	SUPPLEMENT
1) Know the main regions of the electromagnetic spectrum in order of frequency and in order of wavelength 2) Know that all electromagnetic waves travel at the same high speed in a vacuum 3) Describe typical uses of the different regions of the electromagnetic spectrum including: (a) radio waves; radio and television transmissions, astronomy, radio frequency identification (RFID) (b) microwaves; satellite television, mobile phones (cell phones), microwave ovens (c) infrared; electric grills, short range communications such as remote controllers for televisions, intruder alarms, thermal imaging, optical fibres (d) visible light; vision, photography, illumination (e) ultraviolet; security marking, detecting fake bank notes, sterilising water (f) X-rays; medical scanning, security scanners (g) gamma rays; sterilising food and medical equipment, detection of cancer and its treatment 4) Describe the harmful effects on people of excessive exposure to electromagnetic radiation, including: (a) microwaves; internal heating of body cells (b) infrared; skin burns (c) ultraviolet; damage to surface cells and eyes, leading to skin cancer and eye conditions (d) X-rays and gamma rays; mutation or damage to cells in the body . 5) Know that communication with artificial satellites is mainly by microwaves: (a) some satellite phones use low orbit artificial satellites (b) some satellite phones and direct broadcast satellite television use geostationary satellites.	6) Know that the speed of electromagnetic waves in a vacuum is 3.0 × 10^8m/s and is approximately the same in air . 7)Know that many important systems of communications rely on electromagnetic radiation including: (a) mobile phones (cell phones) and wireless internet use microwaves because microwaves can penetrate some walls and only require a short aerial for transmission and reception (b) Bluetooth uses low energy radio waves or microwaves because they can pass through walls but the signal is weakened on doing so (c) optical fibres (visible light or infrared) are used for cable television and high-speed broadband because glass is transparent to visible light and some infrared; visible light and short wavelength infrared can carry high rates of data 8) Know the difference between a digital and analogue signal 9) Know that a sound can be transmitted as a digital or analogue signal 10) Explain the benefits of digital signalling including increased rate of transmission of data and increased range due to accurate signal regeneration