Science Exam Sem 2

Electromagnetic spectrum

shorter waves = higher frequency, higher energy

longer waves = lower frequency, lower energy

all travel at the same speed

Radio waves

Used to broadcast radio and television

Lowest frequency

Microwaves

Used in cooking, radar, telephone and other signals.

Infrared

Transmits heat from sun, fires, radiators.

Visible light

Makes things able to be seen

Ultraviolet

Absorbed by the skin, used in fluorescent tubes

X - rays

Used to see inside of bodies and objects

Gamma Rays

Used in medicine for killing cancer cells

highest frequency

Colours of the visible spectrum

Red - longest wavelength

Orange

Yellow

Green

Blue

Indigo

Violet - shortest wavelength

Law of Reflection

The angle of incidence = the angle of reflection

Regular reflection

Plane (flat) mirrors reflect light in a regular way (at the same angle).

Diffuse reflection

Most objects reflect irregularly because their surface is NOT perfectly smooth. Light is reflected in all directions.

Wave diagram

crest, amp, trough

Plane diagram

incident ray = reflected ray

Convex mirror diagram

light reflects outwards

Concave mirror diagram

light reflects inwards

How does light pass through different transparent media?

Light refracts in a different direction. This occurs because light travels at different speeds for different media.

Refraction diagram

light refracts towards the normal

Refraction

• As light passes through different transparent medium, light bends.

• This is because as light travels from one medium to another it speeds up or slows down

Rules of refraction

When light enters a more dense medium at an angle it is bent towards the normal (because the light slows down).

When light enters a less dense medium at an angle it is bent away from the normal (because the light speeds up).

Refraction in water

Water is denser

Converging lens

Light refracts inwards - biconvex lens

Diverging lens

Light refracts outwards - biconcave lens

Biconvex lens diagram

light refracts inwards

Biconcave lens diagram

light refracts outwards

Real images

Will be flipped and smaller. This is because the image is beyond the focal point. When light crosses - concave mirror, biconcave lens

Virtual images

An image between the lens and the focal point will be upright and enlarged. When light doesn’t cross - convex mirror, convex lens

Why do objects appear white

when they reflect all of the colours of the spectrum

Why do objects appear black

Objects appear black when all of the colours of the spectrum in light are absorbed

Why does an object appear green

An object appears green because it reflects green and absorbs all other colours

Eye diagram

answers

Cornea function

Clear window, refracts light, helps to focus the light

Pupil function

Hole in the iris, which allows light to enter the eye

Iris function

Coloured, changes size to control the amount of light entering the eye

Lens function

Refracts light to focus image on the retina. Focal length adjusted by ciliary muscles

Retina function

Light sensitive cells (rods & cones) which change light energy to nerve impulses.

Optical nerve function

Takes messages from the retina to the brain

Sclera function

The white, tough outer layer that protects the eye.

Liquid humour function

Watery at the front, jelly at the back, helps to keep eye’s shape and provide medium for light to travel through.

What parts of the eye will a light ray pass through to strike the retina?

To reach the retina, light rays first enter through the cornea, then pass through the pupil (its size regulated by the iris), and finally through the lens which focuses the light onto the retina

How does brightness change the eye in light or darkness?

In bright light, the eye's pupil constricts (becomes smaller) to limit the amount of light entering, while in darkness, the pupil dilates (becomes larger) to allow more light in. This is a reflex action controlled by the iris, which contains muscles that adjust the pupil's size.

Rods

Rods are sensitive to light and dark, shape and movement. They only have one type of light-sensitive pigment.

We use mainly rods when trying to see in a dark room – hence why we don’t really see colour in the dark!

Cones

• Cones aren’t as sensitive to light, but they are each sensitive to one of the three primary colours.

• Cones are used for finer details and seeing colour

• People who are colour-blind will either be missing one type of cone or it is weaker. 

ecosystem

Involves the interaction of biotic and abiotic things in a given area, contains habitats where organisms live e.g. forests, deserts, coral reefs

community

Is made of different populations interacting with eachother e.g. forest (trees, bears, funghi)

population

a group of the same species of organisms

e.g. a herd of zebras, a school of fish

biotic factors

living factors

abiotic factors

non living factors

Leaf diagram

Leaf structure and functions

Palisade mesophyll - contain chloroplast

Stomata - allow carbon dioxide to enter and oxygen to be released

Spongy mesophyll - gaseous exchange

Phloem - transports food from the leaves to the rest of the plant

Xylem - transports water from the roots to the leaves

Guard cells - open and close the stomata

Process of photosynthesis

photosynthesis occurs in the chloroplasts of the mesophyll. Chloroplast absorbs light energy from the sun, when combined with carbon dioxide and water, it traps this energy in the chemical bonds of glucose.

Chemical equation

CO2+H2O = C6H12O6O2

Carbon dioxide + water with the sunlight make glucose + oxygen

Cellular respiration

The process of converting stored energy into usable energy. It occurs in the mitochondria.

Process of cellular respiration

The energy stored in plants (as glucose) is released as a molecule called ATP

Chemical equation

Oxygen + glucose = carbon dioxide + water + ATP

aerobic respiration

Produces more ATP

Occurs in mitochondria

Produces carbon dioxide and water as a waste product

Requires oxygen

Used when heart rate and breathing rate rise

anaerobic respiration

Doesn’t require oxygen

Occurs in cytoplasm

Used in the first 1 - 2 minutes of exercise

Produces less ATP

Produces lactic acid as a waste product (animals)

aerobic equation

Glucose + oxygen = Carbon dioxide + water + ATP

anaerobic equation

Glucose = lactic acid + ATP

(lactic acid broken down by liver)

Anaerobic respiration (funghi, yeast and bacteria)

Glucose = ethanol + carbon dioxide + ATP

food chain

feeding relationship

food web

Shows all the connections between the food chains, it has multiple paths

Energy loss and transferal

Only ten percent is passed from each level

producers vs consumers

Producer - organisms that can photosynthesise

Consumer - Primary consumers eat producers

Secondary consumers eat primary consumers

role of decomposers

Break down dead organic matter into simpler inorganic substances.

Factors that disrupt ecosystems

Natural disasters and human activities

The Carbon Cycle

Carbon cycle examples

CO2+H2O = C6H12O2

C6H12O6+O2 = H2O+CO2+ATP