1. A 5-cm high object is placed 5 cm from a 15-cm focal length konvergéieren lens. Determine the image Distanz, the magnification of the image, the image height and der properties of d'Bild.
Bekannt:
Brennwäit (f) = 15 cm
The plus sign indicates that the focal point is real or the rays pass through the point.
D'Héicht vum Objet (ho) = 5 cm
Distanz zum Objet (do) = 5 cm
Gewënschte : d'Distanz vum Bild, the magnification of image, the image height and the properties of image
Léisung:
Formation of image by converging lens :

D'Distanz vum Bild (di):
1/di = 1/f – 1/do = 1/15 – 1/5 = 1/15 – 3/15 = -2/15
di = -15/2 = -7.5 cm
D'Minuszeechen weist un, datt d'Bild virtuell ass oder d'Strahlen net duerch d'Bild ginn.
D'Vergréisserung vum Bild (m):
m = - di / do = -(-7.5)/5 = 7.5/5 = 1.5
De Pluszeechen weist un, datt d'Bild oprecht ass.
D'Héicht vum Bild (hi):
m =h ani /ho
hi = m ho = (1.5)5 = 10/3 = 7.5 cm
De Pluszeechen weist un, datt d'Bild oprecht ass.
The properties of the image
- Quasi
- oprecht
- The image greater than the object
- The image distance is greater than the object distance
2. A 10-cm high object is placed 30 cm from a 15-cm focal length konvergéieren lens. Determine the image distance, the magnification of the image, the image height and der properties of d'Bild.
Bekannt:
Brennwäit (f) = 15 cm
The plus sign indicates that the focal point is real or the rays pass through the point.
D'Héicht vum Objet (h) = 10 cm
Distanz zum Objet (s) = 30 cm
Gewënscht: The image distance, the magnification of the image, the image height and the properties of the image
Léisung:
Formation of the image by the converging lens :

D'Distanz vum Bild (di):
1/di = 1/f – 1/do = 1/15 – 1/30 = 2/30 – 1/30 = 1/30
di = 30/1 = 30 cm
The plus sign indicates that the image is real or the Röntgenopnamen pass through the image.
D'Vergréisserung vum Bild (m):
m = - di / do = -(30)/30 = -30/30 = -1
D'Minuszeechen weist un, datt d'Bild ëmgedréint ass.
D'Héicht vum Bild (hi):
m =h ani /ho
hi = m ho = (-1)10 = -10 cm
D'Minuszeechen weist un, datt d'Bild ëmgedréint ass.
The properties of the image
- real or the rays pass through the image
- invers
- The image height is the same as the object height.
- The image distance is the same as the object distance.
3. A 10-cm high object is placed 30 cm from a 20-cm focal length konvergéieren lens. Determine the image distance, the magnification of the image, the image height and der properties of d'Bild.
Bekannt:
Brennwäit f) = 20 cm
The plus sign indicates that the focal point is real or the rays pass through the point.
D'Héicht vum Objet (h) = 10 cm
Distanz zum Objet (do) = 30 cm
Gesicht: D'Distanz vum Bild, the magnification of image, the image height and the properties of image
Léisung:
D'Distanz vum Bild (di):
1/di = 1/f – 1/do = 1/20 – 1/30 = 3/60 – 2/60 = 1/60
di = 60/1 = 60 cm
The plus sign indicates that the image is real or the rays pass through the image.
D'Vergréisserung vum Bild (m):
m = - di / do = -(60)/30 = -2
D'Minuszeechen weist un, datt d'Bild ëmgedréint ass.
The image is 2 times greater than the object.
D'Héicht vum Bild (hi):
m =h ani /ho
hi = m ho = (-2)10 = -20 cm
D'Minuszeechen weist un, datt d'Bild ëmgedréint ass.
The properties of the image
- real
- invers
- the image height is greater than the object height
- the image distance is greater than the object distance
4. Based on the figure below, determine the focal length of the converging lens!
Bekannt:
Objet Distanz (do) = 20 cm
Bilddistanz (di) = 30 cm
Gewënschte : Brennwäit (f)
Léisung:
1/do + 1/di = 1/f
do = object distance (plus Zeechen well rays pass through Objet)
di = Fernbild (plus Zeechen well rays pass through Bild)
f = an Brennwäit (plus Zeechen because rays pass through the focal point or the focal point is real)
The focal length :
1/f = 1/20 + 1/30 = 3/60 + 2/60 = 5/60
f = 60/5 = 12 cm
5. Object’s distance is 30 cm and the focal length is 20 cm. Determine the magnification of the image.
Bekannt:
The focal length of the converging lens (f) = 20 cm
The plus sign indicates that the focal point is real or rays duerch goen d'Bild.
Objet Distanz (do) = 30 cm
Gesicht: D'Vergréisserung vum Bild (M)
Léisung:
Image distance :
1/di = 1/f – 1/do = 1/20 – 1/30 = 3/60 – 2/60 = 1/60
di = 60/1 = 60 cm
Vergréisserung vum Bild:
M = di / do = 60 cm / 30 cm = 60/30 = 2 Mol
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