How can X-rays see through our bodies? JOYCE CHAN St Mary's Canossian College X-rays are highly penetrating electromagnetic radiation that can pass through objects and produce shadow images on a fluorescent screen. Hard X-rays have higher frequencies and are more penetrating; soft X-rays have lower frequencies and are less penetrating. Discovered in 1895 by German physicist Wilhelm Roentgen, X-rays provide an image of the body's interior when they pass through it and strike a photographic plate or fluorescent screen. Denser materials absorb more X-rays and appear brighter. Today, X-rays are commonly produced in a highly evacuated glass bulb, called an X-ray tube, which contains two electrodes - an anode made of platinum, tungsten or another metal with a high melting point, and a cathode. When a high voltage is applied between the electrodes, streams of electrons (cathode rays) are accelerated from the cathode to the anode and produce X-rays as they strike the anode. The films created by X-rays show different features of the body, including bones, in various shades of grey. By introducing various substances into a patient's body, visibility on images can be improved by creating greater contrast. This is usually done when X-rays of the stomach are taken. How did carnivals start? The word carnival is thought to derive from the Medieval Latin carnem lavare or carnelevarium meaning 'the taking away of meat'. It is associated with the period before Lent in Catholic tradition. During the 40 days before Easter, known as Lent, faithful Catholics devoted themselves to prayer and fasted. Before subjecting themselves to the hardships of Lent, people got into the habit of thoroughly enjoying themselves first with food, drink, festivities, song and dance. They would also try to finish all the rich foods in the house so that they would not be tempted to eat them during Lent. 'Mardi Gras,' the carnival celebrated in New Orleans, United States, means 'fat Tuesday', referring to Shove Tuesday, the day before the start of Lent, when people would attempt to eat up all their remaining stocks of eggs, butter, oil and sugar. This is why pancakes - which use all these ingredients - are popular on Shrove Tuesday, also known as Pancake Day. Over the centuries, carnivals have played a significant role in the development of popular theatre, songs, folk dances and other forms of entertainment. Perhaps, the most well-known carnival of modern times is the annual pre-Lenten one in Rio de Janeiro, Brazil. It is famous for fabulous masked balls, parades with extravagant costumes and wild partying.