Which one among the following is the primary reason for asking persons undergoing X-ray imaging to remove metallic objects?
- A.Metallic objects can absorb/reflect X-ray resulting in dark/bright spot
- B.Metallic objects can melt causing serious skin damage
- C.X-ray can create sparks on hitting the metallic objects
- D.X-ray can damage the metallic objects by altering their composition
Correct answer
Explanation
The correct answer is A, Metallic objects can absorb/reflect X-ray resulting in dark/bright spot. Metal blocks X-rays far more strongly than body tissue, so it spoils the picture.
An X-ray image is a shadow picture. Soft tissue lets most rays pass and appears dark, while bone, which contains calcium, absorbs more and appears light. Metals such as a chain, a belt buckle or a coin have high density and high atomic number, so they stop almost all the rays and leave a sharp bright patch, with streaks around it, that can hide or imitate an injury. Removing them keeps the image clear and avoids a repeat exposure.
B is wrong because a diagnostic X-ray dose carries very little energy and cannot melt metal. C is wrong because X-rays do not make sparks on striking metal. D is wrong because X-rays do not change the chemical composition of ordinary metal objects.
Exam tip: X-ray contrast depends on absorption: dense, high atomic number matter (bone, metal, barium) looks bright on the film.
Practice Questions
View allWhich one of the following metals is used in the filaments of photo-electric cells that convert light energy into electric energy ?
- A.Tungsten
- B.Copper
- C.Rubidium
- D.Aluminium
Show answer
Rubidium, an alkali metal like caesium, gives off electrons easily when light falls on it, so it is used in photoelectric cells.
Read the full explanation →Tooth enamel is made up of which one of the following calcium compounds ?
- A.Calcium carbonate
- B.Calcium sulphate
- C.Calcium hydroxide
- D.Calcium phosphate
Show answer
Tooth enamel is made mainly of calcium phosphate in the form of a hard crystal called hydroxyapatite. Enamel is the hardest substance in the human body, harder even than bone.
Read the full explanation →Which one of the following viruses used to be responsible for highly infectious disease Smallpox ?
- A.Adenovirus
- B.Variola virus
- C.Aichi virus
- D.Coxsackie virus
Show answer
Smallpox was caused by the variola virus, a large DNA virus of the pox family that spread from person to person through the air.
Read the full explanation →After fertilization, the fruit and the seed are produced by
- A.ovule and ovary, respectively
- B.ovary and ovule, respectively
- C.ovary, no ovule required
- D.ovule, no ovary required
Show answer
After fertilisation the ovary of the flower grows into the fruit, and each ovule inside it develops into a seed.
Read the full explanation →Which among the following statements with respect to carbon is/are correct?
1. Carbon forms the basis for all living organisms and many things we use
2. Carbon shows tetra-valency and the property of catenation
3. Carbon forms covalent bonds with itself and other elements
4. Carbon forms compounds containing triple and tetra bonds between carbon atoms
Select the correct answer using the code given below :
- A.1 only
- B.1 and 2 only
- C.1, 2 and 3
- D.2 and 4
Show answer
Statements 1, 2 and 3 are true, but carbon never forms a quadruple, or tetra, bond between two carbon atoms.
Read the full explanation →