Sabtu, 30 Januari 2010

sound and hearing

Sound and Its Properties

Sound produced by vibration.

Sound travel in straight path.

Sound travel in medium.

Sound cannot travel through vacuum.

Sound can be reflected and absorbed.

Properties of Sound-Vibration

Sound produce by vibration.

When an object vibrates, its kinetic energy is changed into sound energy.

Kinetic energy- sound energy

Properties of Sound- travel in medium

Transfer in form of sound waves.

Sound travel through medium solid, liquid, and gas.

Speed of transfer in different medium-increasing speed from gas –liquid-solid

Particle in the solid are very compact, thus the sound vibration can pass very quickly from particle to particle

Properties of Sound -Sound cannot travel through vacuum.

Because there is no atmosphere in moon, outer space. Sound need medium to travel. But outer space is just vacuum space without medium for sound to travel.

Sound cannot travel through vacuum.

Properties of sound- sound reflection

Sound can be reflected by surface-produce echo

Hard surface reflects sound better than soft surface

Ex: Walls of buildings, tunnels, glass, metal

Properties of sound-sound absorption

Reflected sound is always weaker than the original sound because part of the sound energy has been absorbed by the reflecting surface.

Sound can be absorbed by a surface.

Soft surface is better absorber of sound.

Ex: carpets, curtains, cotton, sponge, rubber, soft board.

The soft cushions and padding in car absorb sound from engine.

Application of sound reflection

Determine the depth of sea

Detect the fish in sea

Detect the petroleum in ground

Guide the flight of bats and movement of dolphin (night).

Defects of Hearing

Hearing defects means ear is not working correctly or as well as it should.

It may occur in more than one part of the ear.

1. DEAF-full or partial decrease in the ability to detect or understand sounds.

Deaf usually caused by :

- Eardrum is torn-cannot function

- Ossicle bone fused together-can’t vibrate

- Auditory nerve damaged by loud sound

- Cochlea damage due to sickness/ drugs

2. Temporary hearing loss-build-up of earwax

3. Presbycusis- hearing loss related to aging and other factors.

Correcting hearing defects

Syringes and warm water –remove wax

Replace damaged ossicles

Surgery- damaged eardrums

Electronic gadgets - implantation

Limitation of Hearing

Definition: The range of sound that human can hear. 20-20000Hertz

Limitations of hearing varies with people

Range of hearing in different individual

Children have eardrums that are more elastic. As a result, they can hear better.

As people age, their hearing deteriorates. Their eardrum become less elastic. The range of sound frequencies that they can detect decrease. Their ability to hear high-pitched sounds decrease.

Person exposed to constant loud noise experiences a loss of hearing-range of hearing is smaller than normal people.

Devices to enhance hearing

1. Earphone-Connect the sound from electronic gadgets to ears-change electrical signals into sounds that ear can detect

2. Stethoscope-amplify the sound of heartbeat

3. 3. Microscope-Change soft voice into electrical signals –change into loud voice

Stereophonic Hearing

Definition: The hearing that involves the use of two ears

The sound coming from right will be detected by our right ear slightly earlier than our left ear-produce stronger vibration

The ear nearer to the sources of sound receives:

- The sound earlier than other ear

- Stronger stimulus-impulse-brain-interpret

The louder and the earlier sound detected by our right ear when compared with the softer and delayed sound detected by left ear tells us that the sound comes from the right.

Functions: Enables us to determine the direction of sound accurately

- avoid danger

- Survival of animals

Jumaat, 29 Januari 2010

answer for short exercise book

1. Please write the index.
2. Index for this every exercise is the Italic sentences at the top of each space.

`Sense of sight
1.When someone is said to have blue or brown eyes, which part of the eye is being described? “IRIS”
2.Many animals are actively only at night, would this creature have larger or smaller pupil than human. Why? Bigger. Because in dark, the amount of light is less, so the pupil should enlarge to allow more light to pass into eye.
3.Where are the receptor cells of the eye found? Retina
4.Name the type of receptor cells found in the eye and state its functions. Rod cell- detects motion and sees in dim light Cone cell- detect color
5.Why is the choroid black? This is because it contains of black pigment. This black pigment is use to absorb excess light and prevent light reflection.
6.Which structure provides food to eye? “CHOROID”
7.Name the spot of the retina that a) Most sensitive to light – yellow spot b) Least sensitive to light- blind spot

Light and sight

Reflection and refraction.
1. Compare reflection and refraction.
Criteria to be compare is
a. Dependence on medium
b. Dependence on density
c. Angle of incidence and reflection/refraction
d. Direction of light reflected/refracted

Dependence on medium
Reflection occur in one medium
Refraction occur only when pass through 2 medium

Dependence on density
Reflection Does not depend on the density of medium.
Refraction Depend on the density of the medium

Angle of incidence and reflection/refraction
Reflect- Angle of incidence same with the angle of reflection.
Refract- Angle of incidence different from the angle of refraction.

Direction of light reflected/refracted
Reflect-Light reflected in the opposite direction.
Refract- Light does not refract in the opposite direction.

2.How can light reflection help us to prevent from danger?
Mirror on the car can help us to see others’ car and this can prevent us from accident. A convex mirror is placed at the bend on the road so that drivers can see around the bend.

3.State the instruments that apply the concept of light reflection. Mirror, kaleidoscope, periscope

4.Describe how twinkling of star related to light refraction. Multiple refraction of light happens on different layer of the atmosphere surrounding the Earth. The refraction in random direction makes the rays enter our eye in certain moment only. This leads to sometimes you see the light, sometimes you don’t see the light. Our brain will interpret this situation as “twinkling”.

5.Identify 3 effects of light reflection in our life. -We can see our self through mirror. -We can see the beautiful view reflected on the water. -Doctor can examine patient’s teeth using dental mirror.

6.When the stream of light from a less dense medium goes into denser medium by angle of 90, will the light be refracted? No.

long book experiment

1.Write your report following correct order:
Questions and Answers
2.Draw the picture also.

Textbook Page 24, Activity 1.9
Hypothesis: The light bounce as it hits the mirror.
Answer: The light bounce as it hits the mirror surfaceConclusion: Light can be reflected

Textbook Page 25, Activity 1.10
Hypothesis: Light bend as it travels between medium with different density
1. Yes.
2. Vitreous humour ,eye lens, aqueous humour
Conclusion:Light is refracted or bent when it pass from one medium to another medium with different density.

Textbook Page 29, Activity 1.12
Hypothesis: at certain distance from the eye, the black dot disappears.
Material: figure 1.40 in science textbook
Observation: The dot disappear at certain distance
Answer:1. No
2. No
3. Answer no provided. Do it yourself.
When image falls on the blind spot, the image cannot be seen.

Textbook Page 16, Activity 1.6
1. No need to do part A and B, only do part C
2. Answer question 3 and 4 only.
3. Draw the picture also.
Hypothesis: Sound reflected more when it hits the hard surface.Sound absorb more when it hits the soft surface.
Observation: 1. The reflected sound is clearer when it hits the concrete wall.
2. The reflected sound is soft when it hits the styrofoam wall.
3. Reflection
4. styrofoam

Textbook page 19, activity 1.7
Hypothesis: Hearing with two ear enable people to detect the direction of the sound more accurate compare to hearing with one ear.
Answer: Do it yourself
Conclusion: Hearing with two ears enables us to accurately tell which direction a sound is coming from.

Devices to overcome the limitations of sight.

Devices to overcome the limitations of sight.
1. Microscope
•Instrument to magnify object such as virus.
•Objective lens and eyepiece magnify image.Types- light microscope, electron microscope

2. Magnifying glass
•Limited magnifying power-10 to 15 times
•Use to see small object.
•Magnifying glass is convex lens.

3. Telescope
•viewing distant objects -stars, planets , Moon.
•Consists of two convex lenses- objective and eyepiece lens.
•The image produced by the objective lens is magnified by the eyepiece lens.

4. Binoculars
•Binoculars provide a stereoscopic vision of distant objects.
•The parts of the binoculars and their functions are the same as those of the telescope.
•Binoculars are actually a pair of telescope.
•Use- watch horses running in a race

5. Ultrasound scanning device
•ultrasonic waves - create images -organ , fetus.
•Device shaped like microphone is pressed against the area being scanned.
•This device sends out very high frequency sound waves into the area being scanned.
•The waves bounce back upon hitting an organ and an image of the organ is then obtained on computer screen

6. X-rays
•X-rays can also be used to detect the condition of certain organs or detect fracture of bones.In medical X-rays, the X-rays penetrate the internal soft body tissues and form images on a film which can be examined by a radiologist

Stereoscopic, monocular vision

Comparison between monocular and stereoscopic

Stereoscopic vision
•Both eyes at the front of the head-usually predator, carnivore
•Each eye receives a slightly different image from the other.
•The brain combines two images together and allows the observer to see a 3-dimensional image.
•Human eyes have an overlapping field of viewof about 120�. It is only in this field that we have stereoscopic vision. Beyond this 3-D area, out to 160-180�, we see things only in two dimensions (2-D)--i.e., flat without depth.

Monocular vision
•Seeing with one eye.
•One eye in each side of head
•Mostly herbivore

limitation of sight

Optical illusion
Optical illusion

Limitation of Sight

A. Blind spot
•At certain distance from the eye, some object that you can see previously may disappear, after certain moment, it will reappear.
•This phenomenon occurs because the image of the object has fallen onto the blind spot in your eye.
•This blind spot does not have any photoreceptors. As result, the image of the cross that falls on this spot cannot be detected, and that's why you can't see it.

B. Optical illusion
•Optical illusion are caused by disturbances to the nerve impulses going to the brain.
•The disturbances may caused by the object or condition around the object.
•The brain cannot accurately interpret the information sent by the receptors in eye.
•That’s why you will incorrectly interpret what you actually see.

vision defect

Normal Vision
•Normal vision can see both near and distant object clearly.
•The thickness of the eye lens changes when near and distant object are focussed-accomodation
Several types of vision defects
•Colour blindness

It is caused by irregular surface of cornea, or lens that is not evenly curved.
•Hence, the rays from the image cannot be focused at the same time.
•Thus, the image formed is not very clear.
•Correction: Glasses with cylindrical lenses, special contact lenses, or surgery.

Colour blind
•Our photoreceptor on retina consist of rod(detect brightness) and cone( detect color) cell.
•Cause : Inherited shortage of cone (color receptor)cells. It may also occur because of eye, nerve, or brain damage, or exposure to certain chemicals.
•Effect: Cannot see all or some colors. Most cannot differentiate between red and green

•Cause: Aging-eye lens becomes harder and less elastic, muscles in the ciliary body also lose their ability to contract and relax.
•Effect: Both near and far objects cannot focused.
Correction: Glasses with bifocal lens