Light and Optics

Convex Mirrors

Convex:
A convex mirror is a mirror that comes out towards the source of light, like depicted in the diagram. Convex mirrors have many uses, such as the passenger side mirror of a car. In a convex mirror problem, the image created by the light passing through the mirror is always upright, smaller, and virtual.

This diagram shows how the incident ray hits the mirror at an angle that reflects off upwards. The reflected ray reflects off, but the image is still created behind the mirror, which is why the image is virtual. The actual light rays never touch each other. 

This picture of a passenger side mirror of a car shows how the convex mirror makes images appear closer than they actually are. The mirror allows the driver to see more of his surroundings, but produces a virtual image, skewing the actual placement of the car. 

Tuning Fork and Palm Pipe Lab

Tuning Fork and Palm Pipe Lab
     Sound was the main topic of discussion in class this week. Although I wasn't here for the first half of the lab, the second half of the lab consisted of measuring the length of a palm pipe, measuring the diameter of the pipe, and finally solving the wavelength of the palm pipe. The palm pipe I got was .058m, so the wavelength was .247m. After plugging my numbers into the equation velocity=frequency times wavelength, I was able to solve the frequency, which was 1388.66hz.

My Palm pipe, number 15, note F6.

All of my group's palm pipes together. 

To end the lab, the whole class played their palm pipes to the tune of "Twinkle Twinkle Little Star" with their respective notes.

Lemon Battery Lab

Lemon Battery Lab
In class, we made our own batteries consisting of lemons, pennies, and nails.

Real World Connection:
On the website http://www.apple.com/batteries/, it talks about how the iPad battery works.
iPad batteries are: made of lithium ion, light but give a long life, and not required to be charged fully.
On the graph on the website, the term voltage was something I noticed quickly. In class, we learned that voltage is the electric field surrounding a charged object.  

Projectile Motion

Projectile Motion Lab:
     A projectile is an object with only the force of gravity acting upon it. After going down to the gym and recording the path of a basketball being shot, we tracked the flight on the Video Physics app.

 In this graph, we can derive that the slope of the basketball is constant while the distance over time steadily increases.












In this graph, we can see that the basketball moved in a parabolic shape. The peak of the graph is the moment in which the basketball was as complete rest.

Magnetism

Magnetism:
How can objects like the earth and metals be permanent or temporary magnets?

Objects like the earth and metals can be permanent or temporary magnets depending on their domains. A magnetic domain is a part of a material that determines its magnetism. One example of an item with no domains would be a piece of paper. A piece of paper has no domains, and therefore it can never be magnetic. An object that has domains, but those domains are not lined up would be a paper clip. The paper clip's domains are not lined up until a magnet comes along and aligns its domains, making it magnetic. And finally, an object with domains that are always lined up would be the earth. The moving metals inside of the earth create a magnetic field, and charges on the outer core moving like a solenoid create a huge, permament magnetic field.

iPad Batteries

iPad Batteries

Real World Connection:

The battery used in Apple's iPad is an internal rechargeable lithium-ion polymer (LiPo) battery. This battery is very popular and is found in many laptops and other technology because of its size, power, and lifespan. 

http://www.apple.com/batteries/

This Apple website talks about the use of LiPo's in iPads. 

A typical iPad battery.

The LiPo contains a temperature gague, which tells when the battery is either above or below safe temperature. LiPo batteries givethe best battery life possible with the lowest total weight. They are rechargeable whenever, and they do not require a full charge. LiPo's can be charged many times, as stated in the article. An LiPo produces 3.7 volts per cell, while a AA battery only produces 1.5 volts. The more volts, the more electric potential energy, the more item use!

When a lithium-ion battery like this one is charged, the voltage increases, creating a mountain of positive charge. The electrolytes then move to the negative electrode. When the charge is unplugged, the electrolytes return to the positive electrode.

Forces in 2D and Circular Motion

Big Questions:

What does it mean to analyze forces in 2D?

• Forces analyzed in 2D have a length and a width
• 2D forces have an x as well as a y axis

How do forces cause objects to move in a circle?

• The center pointing (centripetal) forces make objects move in a circle. 
• When an object is moving in a circle, it is accelerating. The object is acceleration because acceleration = a change in velocity over a change in time. Velocity is a vector, and therefore changes. If velocity changes, the object accelerates.

This represents the equation for acceleration. 

• What does it mean to be in orbit? 
• When an object travels around another object as a result of the centripetal force. 

• How do satellites orbit planets? 
• Very similar to the way a plant is able to orbit the sun, satellites are able to orbit a planet. The speed of the satellite is adjusted when it orbits the planet so that it falls to earth at the same rate that the curve of the earth falls away from the satellite. 
• According to Newton's 1st law, there is an equal and opposite force for each force. The Earth pulls on the satellite and the satellite pulls on the Earth. Since there is no air resistance, the satellite continues falling into orbit around the earth.

• How do planets orbit the sun?
• The earth is able to rotate in orbit around the sun due the sun's centripetal force. However, even though the speed is constant, the direction is not. As a result the planets accelerate around the sun. The gravity of the sun acts as on the planets as the centripetal force that keeps them in orbit. Even though the planets and the sun's gravity both pull on each other, the planets orbit around the sun because it has more mass. The planets then fall around the sun because they are both curved.