X-rays

1. What is it?

X-rays are a type of radiation. Radiation is a general term that refers to any sort of energy that can travel through space as either a wave or a particle. Examples of other types of radiation include: light, radio waves, and microwaves. X-rays have more energy than light-rays so they are able to penetrate and travel through materials that light-rays are unable to penetrate and travel through.

X-rays was first discovered by William Roentgen while experimenting with a cathode radiation. In radiography, X-rays that pass through the object expose the film to produce an image. Differences in the types and amounts of the materials that the X-rays must travel through are responsible for the details of the radiographic image.

Since film is sensitive to x-rays in the same way that it is to light-rays, X-rays can be used to produce images. X-rays that are sent through an object can produce an image on a piece of film placed on the opposite side of the object. These are but some examples which uses X-rays: X-rays can be used to kill bacteria which will causes food to spoil. This method was useful for astronauts who went to space as it enabled the preservation of food that the astronauts ate while on the moon and in space.

Generally, X-rays can be used to "look inside" an object and to locate defects in materials and dentists, doctors, NDE inspectors, and airport personal are just some examples of people who use X-rays in their jobs.

Source: http://www.nhs.uk/conditions/x-ray/Pages/Introduction.aspx
http://www.ndt-ed.org/EducationResources/HighSchool/Radiography/introxrays.htm

2. What is its wavelength?

X-rays have a wavelength in the range of 0.01 to 10 nanometers.

Source: http://en.wikipedia.org/wiki/X-ray
http://wiki.answers.com/Q/What_is_the_wavelength_of_an_X-ray

3. Does it need a medium?

No, it does not require a medium.

Source: http://www.juniordentist.com/properties-of-x-ray.html

4. What are the advantages/uses and disadvantages/dangers?

Advantages

a. X-rays can be used to produce an image of any body part due to their high frequency.
b. It is also available as a portable x-ray unit and can be used in hospital wards, operation theatres and ICU/emergency rooms.
c. It is less costly when compared to the other imaging modalities like MRI or CT. However, the amount of information obtained is often limited.

Source: http://www.medindia.net/patients/patientinfo/x-ray_advantages.htm
http://www.nhs.uk/conditions/x-ray/Pages/Introduction.aspx

Disadvantages

a. X-rays consist of a type of radiation known as ionising radiation which is high-energy radiation. Exposure to ionizing radiation is harmful to the human body as it can damage the cells of the body and cause mutations in the DNA (deoxyribonucleic acid), which can trigger cancer in later life.
b. Has a relatively low information when compared to other imaging methods.

Source: http://www.medindia.net/patients/patientinfo/x-ray_disadvantages.htm
http://www.nhs.uk/conditions/x-ray/Pages/Introduction.aspx