OPTION I TEST REVIEW

Transcription

1 IB PHYSICS 3 Name: Period: Date: DEVIL PHYSICS BADDEST CLASS ON CAMPUS OPTION I TEST REVIEW s2. This question is about defects of hearing. The graph below shows an audiogram for a person who has not been exposed to high noise levels hearing loss / db frequency /khz Suggest the hearing defect from which the person is suffering.... A person with normal hearing can detect a sound of intensity W m 2 at a frequency of 3.0 khz. Use data from the graph to determine the minimum intensity at 3.0 khz that can be detected by the person with the hearing defect. (c) On the graph, draw a second line to illustrate the hearing loss caused by many years of exposure to high noise levels in the workplace. Page 1 of 16

2 s3. This question is about sound and hearing. State the approximate range of frequencies that are audible to a person with normal hearing.... Outline the mechanism by which different frequencies are distinguished in the cochlea (c) A person with normal hearing can just hear a sound of intensity W m 2 at a frequency of 1000 Hz. (i) A sound wave of frequency 1000 Hz incident on the ear drum has an intensity of W m 2. Calculate the sound intensity level at the ear. (ii) Explain why the response of the ear is measured as a change in sound intensity level rather than a change of intensity of sound. s6. This question is about sound and hearing. The following graph shows the variation with frequency of the threshold of hearing for Frank and for Albert. Page 2 of 16

3 sound intensity level / db Albert Frank frequency / Hz A sound source produces a note of frequency 70 Hz. The sound power output of the source is W. The sound is emitted uniformly in all directions. Frank and Albert both walk towards the source. Frank stops when he first hears the sound. Albert stops when he first hears the sound. Use the graph to state and explain whether Albert or Frank stops closest to the source. (c) Deduce that the distance from the speaker at which Frank first hears the sound is 46 m. You may assume there is no reflected sound. The surface area of a sphere of radius r is 4 r The frequency of the sound emitted by the source is changed to 4000 Hz while Albert remains at the same location as he was in, and the power output is maintained at the same level as in. Use the graph to state and explain the changes, if any, of the loudness of the sound heard by Albert Page 3 of 16

4 s7. This question is about hearing. State the range of frequencies audible to a normal adult human ear. (c) (d) (e)... Outline the role of the middle ear in the detection of sound Strctures within the cochlea have different lengths and stiffness. Outline how these structures enable different frequencies present in a sound wave to be distinguished Explain how speech discrimination can be affected by changes in the functioning of the cochlea A person with defective hearing can hear sounds with a minimum intensity of W m 2 at 3.0 khz. Determine the loss of hearing in db of this person at this frequency Page 4 of 16

5 s8. This question is about hearing. A sound wave of intensity W m 2 produces a pressure variation on the eardrum. Calculate the sound intensity level of the sound wave at the eardrum. (d) (e) Describe how the sound pressure is amplified in the middle ear Explain how speech discrimination can be affected by changes in the functioning of the cochlea A person with defective hearing can hear sounds with a minimum intensity of W m 2 at 3.0 khz. Determine the loss of hearing in db of this person at this frequency Page 5 of 16

6 s9. This question is about sound and hearing. Distinguish between conductive and sensory hearing loss. Conductive: Sensory: The diagram below shows a sketch of the variation with frequency f of the intensity level IL of sound heard by a young person with normal hearing Intensity level/d B (c) Frequency/Hz On the diagram sketch the variation with f of the IL of an elderly person. At a frequency of 3.0 khz a person has a hearing loss of 15 db. For the frequency of 3.0 khz calculate the ratio minimum intensity of sound heard by person with defective hearing minimum intensity of sound heard by person with normal hearing s10. This question is about ultrasound scanning. State a typical value for the frequency of ultrasound used in medical scanning.... The diagram below shows an ultrasound transmitter and receiver placed in contact with the skin. Page 6 of 16

7 d ultrasound transmitter and receiver O l layer of skin and fat The purpose of this particular scan is to find the depth d of the organ labelled O below the skin and also to find its length, l. (i) Suggest why a layer of gel is applied between the ultrasound transmitter/receiver and the skin. On the graph below the pulse strength of the reflected pulses is plotted against time t where t is the time lapsed between the pulse being transmitted and the time that the pulse is received. pulse strength / relative units A B D C t / s (ii) Indicate on the diagram below the origin of the reflected pulses A, B and C and D. d ultrasound transmitter and receiver O l layer of skin and fat Page 7 of 16

8 (c) (d) (iii) The mean speed in tissue and muscle of the ultrasound used in this scan is ms 1. Using data from the above graph, estimate the depth d of the organ beneath the skin and the length l of the organ O. The above scan is known as an A-scan. State one way in which a B-scan differs from an A-scan State one advantage and one disadvantage of using ultrasound as opposed to using X-rays in medical diagnosis. Advantage: Disadvantage:... (4) s12. This question is about medical imaging.... State and explain which imaging technique is normally used (i) to detect a broken bone. (ii) to examine the growth of a fetus. Page 8 of 16

9 The graph below shows the variation of the intensity I of a parallel beam of X-rays after it has been transmitted through a thickness x of lead. I / arbitrary units (i) Define half-value thickness, x / mm x 1. 2 (ii) (iii) (iv) Use the graph to estimate x 1 for this beam in lead. 2 Determine the thickness of lead required to reduce the intensity transmitted to 20% of its initial value. A second metal has a half-value thickness x 1 for this radiation of 8 mm. Calculate what 2 thickness of this metal is required to reduce the intensity of the transmitted beam by 80%. Page 9 of 16

10 s13. When X-rays are used for diagnostic purposes, beam energies of about 30 kev are used. This results in good contrast on the radiogram because the most important attenuation mechanism is not simple scattering. Outline the most important attenuation mechanism that is taking place at this energy Explain the following terms. (i) Attenuation coefficient (ii) Half-value thickness (c) The attenuation coefficient at 30 kev varies with the atomic number Z as shown below. Attenuation coefficient Z 3 The data given below list average values of the atomic number Z for different biological materials. biological material atomic number Z fat 5.9 muscle 7.4 bone 13.9 (i) Calculate the ratio attenuation coefficient for bone attenuation coefficient for muscle Page 10 of 16

11 (ii) Suggest why X-rays of 30 kev energy are useful for diagnosing a broken bone but a different technique must be used for examining a fat-muscle boundary. s15. This question is about X-rays. (4) State what is meant by X-ray quality A parallel beam of X-rays of intensity I 0 is incident on a material of thickness x as shown below. The intensity of the emergent beam is I. I 0 I x Define half-value thickness (c) Using the axes below, draw a sketch-graph to show the variation with x of the intensity I. I 0 I x Page 11 of 16

12 (d) Annotate your sketch-graph to show the half-value thickness x (e) State the name of one of the mechanisms responsible for the attenuation of X-rays in matter.... s18. This question is about the absorption of X-radiation in body tissues. State two attenuation mechanisms by which X-rays are attenuated in body tissue (i) Outline the basis of computed tomography (CT) imaging. (ii) Describe how a standard X-ray photographic image differs from a computed tomography image. Page 12 of 16

13 s19. Nuclear magnetic resonance (NMR) imaging is a technique in which protons inside the patient are made to emit an electromagnetic signal. Outline the mechanism by which the signal is emitted by the protons (4) State one advantage to the patient of using NMR imaging compared to X-ray radiography s23. This question is about the use of radiation in medicine. When referring to radiation dosage, α-radiation and γ-radiation have different quality factors. (i) State which type of radiation has the larger quality factor. (ii) Explain why, for the same absorbed dose, the radiations have different effects. The risk factor attached to any particular dose equivalent depends not only on the total dose but also on the dose rate. Explain why the risk factor depends on dose rate Page 13 of 16

14 Iodine-131 is used to label human serum albumin. This isotope has a physical half-life of 8.0 days and a biological half-life of 21 days. (c) Determine the time taken for the activity within the body of a particular dose of this isotope to be reduced to 4 1 of its initial activity s24. A patient of mass 60 kg receives a dose equivalent of 3 30 μsv during a chest X-ray. The quality factor (relative biological effectiveness) of X-rays is 1. (i) Calculate the absorbed dose received by the patient. (ii) Estimate the total energy received by the patient. (c) Outline two precautions that an X-ray machine operator should take to minimize his/her exposure to X-rays State two possible biological effects for an X-ray machine operator of not taking suitable precautions Page 14 of 16

15 X-rays can also be used in radiation therapy. The X-rays used are of a much higher intensity than those used to take chest X-rays. (d) (i) Suggest a situation in which radiation therapy might be used. (ii) Outline the basis of X-radiation therapy. s26. State two mechanisms by which radiation causes damage to cells in the body. For one of these mechanisms, briefly outline how the damage is caused Outline: (Total 3 marks) s27. The effects of ionizing radiation on the human body may become noticeable soon after exposure to the radiation or after many years. Describe and explain how the interaction of radiation with cells may account for these differences (Total 6 marks) Page 15 of 16

16 s28. This question is about the effects of ionizing radiation on the body. The term absorbed dose is used in radiation dosimetry. State three factors that affect the absorbed dose State and explain two possible precautions that can be taken to reduce the exposure of a radiation worker given that the time of exposure cannot be changed s31. This question is about radiation dosimetry. Define exposure A patient is injected with a gamma ray emitter. The radiation from the source creates an exposure in the body of C kg 1. The average energy required to singly ionize an atom in the human body is approximately 40 ev and the quality factor for gamma radiation is 1. Deduce that this corresponds to a dose equivalent of 340 msv Page 16 of 16