Optics & Lenses, Reflection & Refraction and Sexual Reproduction in Man

Optics & lenses
Reflection & refraction
Sexual Reproduction in Man

note: all pictures on this page are done by myself.

Reflection

Regular reflection

When a parallel beam of light hits a flat, smooth and shiny surface, nearly all the light that hits the surface are reflected back as a parallel beam of light. This results in a clear and undistorted image on the surface.

in a regular reflection, angle of incidence = angle of reflection

Irregular reflection

When a parallel beam of light hits a rough surface, the light rays are scattered irregularly or diffused in multiple directions. This means you cannot see any reflected image on the surface. Any light not reflected is absorbed.

Refraction

Light slows down when it travels from one medium to a denser medium. Slower light rays bend towards the normal.

angle of incidence > angle of refraction

Mirrors

Types of mirrors:

• Plane mirrors
• Concave mirrors
• Convex mirrors

Plane mirrors

An image in a plane mirror is:

• formed at the same distance from the mirror as the object
• laterally inverted
• right side up in orientation

Concave mirrors

• reflects a parallel beam of light inwards
• images formed are larger

Convex mirrors

• reflects a parallel beam of light outwards
• images formed are smaller
• wider field of view

Dispersion of light

White light is a mixture of different colours that can be seen when white light is shone through a prism

Colour spectrum

A coloured object under white light will reflect its own colour and absorb other colours. A white object will appear white because white reflects all 3 primary colours, while a black object will appear black it absorbs all colours.

Sexual reproduction in man

Reproduction is the biological processes where new individuals, known as offspring, are made from the older ones, the parents

Sexual reproduction

• biological process of forming a new individual through the fusion of 2 gametes
• fusion process is known as fertilisation
• in cases where 2 gametes are distinct in form and structure, the larger gamete is the egg, while the smaller one is the sperm

Asexual reproduction

biological process of forming a new individual from a single parent without the fusion of gametes

Puberty

developmental process where a child's body matures into an adult body where he or she is now capable of reproduction

Puberty is triggered by:

1. release of hormones from the brain to the gonads (organs responsible for producing sperm and eggs)
2. in response to hormonal signals from the brain, the gonads begin secreting sex hormones (e.g. testosterone and oestrogen)
3. gonads also start gamete production
4. secondary sexual characteristics begin to develop

Secondary sexual characteristics

unique features found in each sex of a species of organisms and only arise in later parts of the organism's life cycle

Males

• 11 - 15 yrs old
• growth of facial, underarm, chest, abdominal and pubic hair
• broadening of chest and shoulders
• enlargement of penis and testes
• sebaceous (oil) and sweat glands become more active
• deepening of voice as larynx enlargens
• increase in muscle mass and strength
• increase in height

Females

• 9-13 yrs old
• growth of underarm and pubic hair
• broadening of hips
• enlargement of breasts
• sebaceous and sweat glands become more active

Sexually Transmitted Diseases (STDs)

STDs refer to:

• diseases transmitted mainly through sexual intercourse
• caused by bacteria and viruses
• affect the reproductive system
• infections can be fatal
• e.g. Syphilis, Gonorrhea, AIDS

Prevention against STDs

• practice monogamy or abstinence
• use condoms during intercourse
• do not abuse drugs
• do not share instruments that may break skin and may be contaminated with blood
• go to reliable practitioners who use sterilised/disposable instruments