Module 5 Flashcards
Peptic Ulcers
20th century Illness which attacked the lining of the stomach
Existing Theory: Caused by poor diet, lack of exercise and stress
Challenging theory: Peptic Ulcers are caused by a bacterial infection
They encounter a serious problem, they could not grow the bacteria in the usual time span, 1-2 days. Samples were left in the incubator for up to 5 days then inspected
This strain of bacteria needed a longer incubation time due to the highly acidic environment
Scientific name: Helicobacter pylori (H. pylori)
Scientific community wasn’t convinced so they digested H. pylori and cured themselves with antibiotics
Plant growth (Von Helmont)
Existing theory: plants grew by easting soil
He weighed a willow tree and weighed dry soil. He planted the tree, watered it and then left it for 5 years. He then re-weighed the tree, which had increased in mass by over 12 stone.
The tree’s matter did not come from soil; it must have gained its matter from the water he had added to it over the years.
Microwaves (Spencer)
at work in 1945 Spencer was standing next to an active magnetron when a candy bar in his pocket melted. Intrigued, he sent out for unpopped popcorn. When it popped in front of the magnetron, he realized that microwaves could cook food.
Heat is the transfer of energy by temperature differences at the micro-scale it is the increased motion of molecules
Eratosthenes and Earths circumference
First estimate of the earths radius to Eratosthenes, in Alexandria, around 240 B.C.E.
Eratosthenes knew of a deep well near Aswan on the Nile where the sun shined all the way to the bottom at noon on the day of the summer solstice. At that day, it was directly overhead at noon. On the same day, Eratosthenesmeasured the shadow of the a stick at noon in Alexandria. The length of that shadow was not zero because the sun was not directly overhead in Alexandria.
Eratosthenes analysed the observations with the assumption that the earth is a sphere and the sun is very far away. The geometry of the situation is sketched at the right. He concluded that the circumference of the earth was about 50 times greater than the distance from Alexandria to Aswan
Doppler and the Doppler effect
the change in frequency of a wave in relation to an observer who is moving relative to the wave source.
1842
A common example of Doppler effect is the change of pitch heard when a vehicle sounding a horn approaches and recedes from an observer. Compared to the emitted frequency, the received frequency is higher during the approach, identical at the instant of passing by, and lower during the recession.
One of the major uses f the doppler effect is the measurement to distant astronomical objects and determining their motion.
Consequence: the universe is expanding as time progresses
Resolution of another theory: Universe had a beginning roughly 13.7 billion years ago
Priestley’s experiments with oxygen
Existing theory: phlogiston, in early chemical theory, hypothetical principle of fire, of which every combustible substance was in part composed. In this view, the phenomena of burning, now called oxidation, was caused by the liberation of phlogiston.
1774, he prepared oxygen by heating mercury oxide with a burning glass. He found that oxygen did not dissolve in water and it made combustion stronger.
Priestley made an enormously important observation. A flame went out when placed in a jar in which a mouse would die due to lack of air. Putting a green plant in the jar and exposing it to sunlight would “refresh” the air, permitting a flame to burn and a mouse to breathe.
Waves
Mechanical waves require a medium (substance) to travel through
Solid (earthquake P&S waves), liquid (ocean waves), and air (sound)
There are two types of waves, transverse and longitudinal
Amplitude: the distance from the null (rest) point to the maximum displacement
Frequency: Number of waves that pass a point per second
Wavelength: the distance from one point on a wave to the matching point on the next wave m
Velocity: the speed and direction of the wave
Period: the time taken for one complete wave to pass a point
The Wave Equation
V= fλ
Velocity= frequency x wavelength
The unique characteristic of electromagnetic radiation bracket EMR bracket is its velocity is fixed in a vacuum as “c” 3×108m/s
What is the velocity of a 1cm microwave.
f=V/λ = 3x108/0.01
= 3x1010
Frequency = speed of light/ wavelength
varp
V – validity (follows scientific method and tests independent variable while keeping controls)
A – accuracy (how are they measured, using accurate measuring technologies e.g. pipet)
R – reliability (repletion to find average)
P – precision (how close the measurements are together, little to no outliers all following the
same pattern)
