launch file doesn't use the parameters

edit

I am a beginner to ROS so am not sure why this is happening.

<launch>
  <node name="hello_world_node" pkg="hello_world" type="hello_world.py" output="screen">
    <param name="freq" value="5" />
    <param name="text" value="Lauch file is working" />
  </node>
</launch>

this is my launch file.

and below is my node hello_world

#! /usr/bin/env python

import rospy
rospy.init_node("hello_world")


#initialising parameters
freq = rospy.get_param('freq',20)
text = rospy.get_param('text',"Hello World")
full_string = text + " %s" %rospy.get_time()
rate = rospy.Rate(freq)
while not rospy.is_shutdown():
    print full_string
    rate.sleep()

now here is the weird part,

if i list out the parameters separately outside the node in the launch file it seems to work.

<launch>

  <node name="hello_world_node" pkg="hello_world" type="hello_world.py" output="screen" />

  <param name="freq" value="0.5" />
  <param name="text" value="Hello World from Launch file" />

</launch>

any idea why the second format works but the first one doesn't?